Advice needed on replacing a ball valve

[Norman Bernstein]

OK, I'm surfacing from the depth of the bilge to ask an actual boat-related question.

I need to replace a ball valve. It's the drain valve for my gravity-drain holding tank... something I rarely use, but don't want to be without. Normally, we get our boat pumped out, either in our home slip, or when we're in a harbor like Great Salt Pond in Block Island.... but when well offshore, we might drain the tank using the valve. Obviously, it's not often used.

The valve itself is a 2" stainless ball valve with female threads (2", or DN50) on both ends... the handle is marked 'MT Full Flow', but I haven't been able to find the manufacturer. The valve is screwed into a thru-hull which has a 90 degree bend, and is positioned just below the waterline.

When I bought the boat (new) in 2005, the valve was very stiff, to turn. All other thru-hulls are similarly protected, by the same type of valve, but in smaller sizes... and they're easy to open and close, but this particular one was not. Over the last 6 years, the valve got progressively harder to turn, and I had to resort to a short length of 1.5" pipe nipple to give me additional leverage.

Last fall, in trying to open the valve, the stem broke.... snapped right off, with the valve in the closed position. The stem itself was apparently made of brass or bronze.

So, the valve needs to be replaced. However, since it is protecting a thru-hull just below the water line, it would normally require a short-haul to do it.. costing around $400. A replacement valve could cost anywhere from $125-$300, depending on type and material.

Yesterday, I was able to remove the sanitary hose from the inside end of the valve, in order to drain it (since the volume of the hose doesn't get evacuated when the tank is pumped out).... not a pleasant task, I assure you, but someone had to do it. Once finished, I could feel the surface of the ball inside the valve... and it feels like it's severely corroded, which is perhaps the reason the valve failed.

I'm wondering, though, if it would be safe to do it in the water. I can easily reach the thru-hull from the outside, and could block it with a wooden plug temporarily. The seal might not be perfect, but I'm guessing it would be good enough to reduce the water flow to a trickle while the valve is unscrewed from the thru-hull, and a new one screwed on.

So, I have the following questions for the crowd:

1) What does everyone think of the safety implications of doing it while in the water?

2) When installing a new valve, would I use teflon tape on the threads, or some other compound?

3) Should I stick with a stainless ball valve... or switch to a Forespar marelon valve? The marelon valve would be cheaper, and I've had good luck with them on previous boats.

Any/all responses welcomed.

[Paul Pless]

I'm wondering, though, if it would be safe to do it in the water.

Any/all responses welcomed.

what's the worst that could happen?

[Norman Bernstein]

what's the worst that could happen?

Hmmmm.... it could leak substantially, and I might not be able to get the valve onto the thru-hull, necessitating an emergency haul-out?

[Jim Ledger]

Make a tapered plug out of cedar or pine and tap it into the hole from the outside.

[Norman Bernstein]

Make a tapered plug out of cedar or pine and tap it into the hole from the outside.

That part is obvious, although the thru-hulls on my boat have a small 'spine' along the inside of the opening... possibly there to accomodate an installation tool to prevent it from turning as the inside piece was screwed in. That little bit of spine (maybe 3/16" tall by 1/8" wide) would interfere with the seal of a wooden plug, unless the plug were soft enough to deform around it.

Of course, there wouldn't be much possibility of 'tapping' it in, since it would be under water by about 6-8" or so. Not sure if swinging a hammer under water would work.

[Paul Pless]

Of course, there wouldn't be much possibility of 'tapping' it in, since it would be under water by about 6-8" or so. Not sure if swinging a hammer under water would work.

we're gonna need video

[Norman Bernstein]

we're gonna need video

Yeah, just what I need. Even better: show up when I do it, so you can stand on the dock, drink beer, and emit snarky comments all the while.... I'm sure you'd LOVE that!

[Dan McCosh]

How about careening the boat at the dock--using the main halyard? As long as you are making a spectacle out of yourself.

[Paul Pless]

Yeah, just what I need. Even better: show up when I do it, so you can stand on the dock, drink beer, and emit snarky comments all the while.... I'm sure you'd LOVE that!

actually i'm not really that kinda guy

[Norman Bernstein]

How about careening the boat at the dock--using the main halyard? As long as you are making a spectacle out of yourself.

Hmmmmm... hadn't thought of that.... good idea! I think I'd have to move the boat, because my mast would crash into a huge megayacht in the slip next to me... and working below would be a bit of a challenge, due to the angle... but it's not a bad idea. I think I'll measure the position of that thru-hull and figure out just how severe the heel would have to be.

[Garret]

That part is obvious, although the thru-hulls on my boat have a small 'spine' along the inside of the opening... possibly there to accomodate an installation tool to prevent it from turning as the inside piece was screwed in. That little bit of spine (maybe 3/16" tall by 1/8" wide) would interfere with the seal of a wooden plug, unless the plug were soft enough to deform around it.

Of course, there wouldn't be much possibility of 'tapping' it in, since it would be under water by about 6-8" or so. Not sure if swinging a hammer under water would work.

The cedar would be soft enough to deform around the spline (which is there to prevent turning, as you surmised). You could add some Rescue tape http://www.rescuetape.com/?gclid=CPi...FQl_5Qod4S-RCA if you want double protection. Swinging a 5 lb. hammer underwater applies plenty of force.

My method would be to go with the best quality all stainless valve I could get. I'm an old fart - I mistrust plastic below the waterline.

[Peerie Maa]

How about careening the boat at the dock--using the main halyard? As long as you are making a spectacle out of yourself.

+1 Or hang the dingy off the boom and fill it with water, that will heel her. Then you can tap in a nice soft plug to guard against wash. Or try a plastic bag with a dollop of expanding foam in it, that will form itself to the inside of the through hull and can be dug out with a screw driver when you are finished.

[Jim Ledger]

Like Garret says, you wouldn't have to hit it in very hard if the fit is close and the taper shallow. See if you can borrow a similar sized thru hull to use to make the plug. If you put the plug in the day before, and the wood is dry, it should swell up overnight.

[Peerie Maa]

Like Garret says, you wouldn't have to hit it in very hard if the fit is close and the taper shallow. See if you can borrow a similar sized thru hull to use to make the plug. If you put the plug in the day before, and the wood is dry, it should swell up overnight.

Steady on lad. He has to pull it out again as well.

[Breakaway]

+ 1 on the tapered plug. You could have another on hand to bung the stem from inside as well if you are a belt-and-suspenders type (Not a bad idea to have one of those tied to each through-hull anyways

As for material selection, I personally dont like mixing threaded fittings. So stainless with ss, bronze with bronze, plastic w/ plastic etc.

My Two Pennies

Kevin

[Norman Bernstein]

My method would be to go with the best quality all stainless valve I could get. I'm an old fart - I mistrust plastic below the waterline.

Well, considering the problems I had with this original valve, which appears to be all-stainless, I'm a bit less sure. I owned a succession of boats with Marelon seacocks from 1985 to 2002... 17 years of experience... and NEVER had a problem with them... they never froze up like the one I'm battling now.

As for material selection, I personally dont like mixing threaded fittings. So stainless with ss, bronze with bronze, plastic w/ plastic etc.

I would agree in principal... although it looks to me as if the 90 degree thru-hull could be bronze, and the valve body looks, to my slip neighbor who is a machinist, to be stainless. The other end of the valve has a plastic hose barb fitting, so it could be that the original system was plastic to stainless to bronze. What I REALLY care about is getting a valve that won't freeze up, and will turn without having to resort to drastic measures, which is how I broke the original in the first place.

[Jim Ledger]

Steady on lad. He has to pull it out again as well.

Well no, once the ball valve is fitted the plug can be knocked out from the inside, then the valve shut.

[Norman Bernstein]

Well no, once the ball valve is fitted the plug can be knocked out from the inside, then the valve shut.

Nope, don't think so... remember, the thru-hull has a 90 degree bend.

[Pete E]

Norman assuming you have the overflow plugged and you are ready to go. Really make sure because Mr. Murphy is always lurking about. The overflow properly pugged and boat back to straight and level makes life easier.

Stainless is the way to go no matter the price. One trick which would have saved the valve you are now replacing is to have a gob of Lithium grease on either side of the ball. You indicated you seldom use it, so that makes more important.

You did not indicate what kind of metal the ball valve screws on too ? If it is stainless, this is the approach found out by myself and others having installed hundreds of valves with out leaks. First we coat the male threads with a product called Anti seize then put teflon tape on the treads follow by more anti seize or a type of pipe dope that has liquid teflon in it. Just teflon tape or pipe dope does seem to be enough all the time. Stainless has a tendency to gall and that is the last thing you want to happen in the place you are at. Don't let any one talk you into cutting corners on this one.

[Jim Ledger]

Nope, don't think so... remember, the thru-hull has a 90 degree bend.

The thru-hull? Or there's a 90 degree tailpieces somewhere. Usually the thru-hull and seacock are in a straight line and any bend in the line occurs inboard.

[Norman Bernstein]

The thru-hull? Or there's a 90 degree tailpieces somewhere. Usually the thru-hull and seacock are in a straight line and any bend in the line occurs inboard.

Not in my boat. The thru-hell itself has the 90 degree bend... at the end of which, the valve is mounted.

[Norman Bernstein]

Norman assuming you have the overflow plugged and you are ready to go. Really make sure because Mr. Murphy is always lurking about. The overflow properly pugged and boat back to straight and level makes life easier.

Good point... I was assuming I'd have to leave the boat heeled while replacing the valve.

Stainless is the way to go no matter the price. One trick which would have saved the valve you are now replacing is to have a gob of Lithium grease on either side of the ball. You indicated you seldom use it, so that makes more important.

I don't see how I'd apply it. I could possibly apply some to the outboard side of the ball, although I'd need a flexible 'dauber' of some sort the make it around the 90 degree bend. I don't see any way to apply any grease to the inside face of the ball, though... the valve connects directly to the sanitary hose that rises up to the bottom of the high-mounted holding tank, and the hose (2" diameter) should be considered to be 'non-flexible', for all intents and purposes. Draining that hose (which I did yesterday) is NOT something I'd want to do again, any time soon.... for reasons which ought to be fairly obvious.

You did not indicate what kind of metal the ball valve screws on too ?

It looks like the 90 degree elbow is made of bronze, although it's not a casting... it looks a bit more like a fabricated piece of tubing... but, then again, with the lighting being lousy in the compartment, and with a bit of oxidation and just plain 'ol dort on it, it could be stainless... I don't know.

If it is stainless, this is the approach found out by myself and others having installed hundreds of valves with out leaks. First we coat the male threads with a product called Anti seize then put teflon tape on the treads follow by more anti seize or a type of pipe dope that has liquid teflon in it. Just teflon tape or pipe dope does seem to be enough all the time.

Was that a typo? Did you mean to say that teflon tape, by itself, is NOT enough?

Stainless has a tendency to gall and that is the last thing you want to happen in the place you are at. Don't let any one talk you into cutting corners on this one.

I'm all too familiar with stainless steel galling.... and it's one of my concerns; the possibility that the valve might NOT come off the tailpiece easily, or without damage. It's also the reason I'm still considering a Marelon valve; 17 years of good experience with the stuff has me reasonably convinced that it's a good choice.... and it won't gall or result in galvanic corrosion.

[Breakaway]

With respect, you should look closer. Never heard of nor seen, a seacock that bent 90 degrees. Check out this pic. The tailpiece on the far left is a "full flow" version. You can see it has a barely perceptible shoulder where it screws in to the 'cock/ Imagine it installed and its not hard to see that it can LOOK like an integral part. BUt its not.

K

[Figment]

Am I the only one here who would rather see a proper seacock rather than a throughhull-tailpiece-valve combo on a penetration below the waterline?

What on EARTH has become of that staunch WBF conservatism I've known and loved?

[Norman Bernstein]

With respect, you should look closer. Never heard of nor seen, a seacock that bent 90 degrees. Check out this pic. The tailpiece on the far left is a "full flow" version. You can see it has a barely perceptible shoulder where it screws in to the 'cock/ Imagine it installed and its not hard to see that it can LOOK like an integral part. BUt its not.

Did I mention that this is a French boat? A Jeanneau? Yup, I bought it from the cheese-eating surrender monkeys, and they have their own way of doing things.

You might be correct... I frankly didn't look all that close, because I didn't see the need to remove the 90 degree elbow. I still don't see any need to remove it.

EDITED TO ADD: I'm going down to the boat tonight, and will take a closer look. Regardless, I do NOT want to change the configuration. The 90 degree bend results in the valve body being located where it's easy to reach... changing that will make life harder, and in the future, I'm going to want to give that valve a LOT more excercise, periodically.

I'll take a few photos, if I can.

[Norman Bernstein]

What on EARTH has become of that staunch WBF conservatism I've known and loved?

Well, I DON'T wear a belt and suspenders at the same time. I like to be conservative, but I don't want to make a fetish out of it.

[Recycled]

If it were my boat I would use a bronze seacock for sewage, particularly if you rarely use it. Stainless has corrosion problems with holding tank waste and the residual sewage trapped on the inside hose is not oxygenated. I would expect a stainless valve to get progressively harder to open as it corroded. If you regularly dumped waste overboard it probably wouldn't be as much as an issue. I went with a salvage store bronze valve on my boat and haven't had any problems.

[Norman Bernstein]

If it were my boat I would use a bronze seacock for sewage, particularly if you rarely use it. Stainless has corrosion problems with holding tank waste and the residual sewage trapped on the inside hose is not oxygenated. I would expect a stainless valve to get progressively harder to open as it corroded. If you regularly dumped waste overboard it probably wouldn't be as much as an issue. I went with a salvage store bronze valve on my boat and haven't had any problems.

That makes sense. In fact, when I bought the boat, I was concerned because the holding tanks are custom fabricated from stainless steel, and I was aware that sewage and stainless don't mix. They told me that the tanks were internally coated with something after fabrication.

After I removed the hose barb and sanitary hose from the inboard side yesterday, I could feel the corrosion on the valve ball.... confirms your suggestion, I think.

[ILikeRust]

I highly recommend the following as required reading whenever replacing a seacock or through-hull fitting:

http://www.pbase.com/mainecruising/seacock_primer

http://www.pbase.com/mainecruising/replacing_thruhulls

[Norman Bernstein]

Well, I see that I can buy a Groco stainless steel 2" ball valve for $134 plus shipping from an online discounter... and the Groco models have a drain plug, so I suspect I can inject lithium grease in through the drain plug from time to time. This is cheaper than a Forespar marelon ball valve (they're $199), and it's all S.S., so I can hold my head up high and scorn the plastic The Groco models have a square drive stem that is replaceable from the outside in the event of breakage, which is what happened to the OEM valve.

[Tobago]

Hmmmm.... it could leak substantially, and I might not be able to get the valve onto the thru-hull, necessitating an emergency haul-out?

I would change "substantially" to disastrously. Is $400 too much to insure the boat doesn't sink? A 2" hole will let a lot of water in before you can pry yourself out of that compartment and get the boat to the travel lift.

As an old DCA and Cheng a single valve to the sea still gives me nightmares.

"Eternal vigilance is the price of safety" (Four or five hundred bucks always helps, too.)

Good luck,
Ted

[Jim Ledger]

How does this system work in reality? It just seems that a gravity powered system draining the goopy, unmacerated contents of a holding tank, around a ninety degree bend, no less, might need some sort of assistance, once the bottom strata starts crowding the exit door.

[Canoeyawl]

Ball Valve Recall... > IBV-FBV SERVICE BULLETIN

GROCO's design for the imported valves series shown above specified a high-grade stainless steel valve stem. We have discovered that the stem material used in some of the valves manufactured between 2004 and 2006 may not have complied with our specifications. Valves with out-of-spec stems may not be suitable for salt-water use. Since the non-compliant silver color stems may fail when the valve is actuated we wish to have all such valves removed from service. GROCO will supply replacement valves at no charge. If your boat hasn't sunk.

(I don't like ball valves as seacocks)

[Norman Bernstein]

How does this system work in reality? It just seems that a gravity powered system draining the goopy, unmacerated contents of a holding tank, around a ninety degree bend, no less, might need some sort of assistance, once the bottom strata starts crowding the exit door.

Actually, it works amazingly well... on the rare occasions when we use it (only well off the coast). The...uhhh....'thickness' of the contents of the holding tank isn't a problem; solids tend to break down, over time, to a sludge, but it's a free-flowing sludge... and the huge 2" diameter samitary hose and free flow valve don't represent an obstruction. When I drained the hose yesterday (which runs about 7 feet, from the bottom of the holding tank, down to the valve), what came out was mostly liquid. At the very end, the 'solids' were of the consistency of a thick gravy (sorry for the imagery, but I'm floundering here for a good example). I've owned this boat for six years, and the hose and valve have never gotten jammed (at least, when I could open the valve).

Of course, we prefer NOT to use it. We pay for a regular pumpout, weekly, at the dock, and in many places we visit, there are free pump-out boats that come around. 18 gallons is actually a LOT of capacity, and the electric head is actually more conservative of flushwater, than the previous manual head. When cruising, that tank is more than good enough for four or five days, if it's just my wife and I.

[Norman Bernstein]

Ball Valve Recall... > IBV-FBV SERVICE BULLETIN

GROCO's design for the imported valves series shown above specified a high-grade stainless steel valve stem. We have discovered that the stem material used in some of the valves manufactured between 2004 and 2006 may not have complied with our specifications. Valves with out-of-spec stems may not be suitable for salt-water use. Since the non-compliant silver color stems may fail when the valve is actuated we wish to have all such valves removed from service. GROCO will supply replacement valves at no charge. If your boat hasn't sunk.

(I don't like ball valves as seacocks)

Yeah, I read all about that... they've fixed the problem.

As far as a genuine 'seacock' is concerned, it wolud make reaching it for access very hard, unless I were to relocate the thru-hull, and I definately don't want to do that.

[Breakaway]

As far as a genuine 'seacock' is concerned, it wolud make reaching it for access very hard, unless I were to relocate the thru-hull, and I definately don't want to do that.

In your OP you stated a desire to avoid a haul. But since you brought replacement up,those groco seacocks have a square hole on the handle so thay can be turned by placing a rachet handle in the hole to extend your reach. Its also easy enough to bolt a length of metal rod to the handle in such a way that you can push and pull on the rod to open/close the valve.

Kevin

[Norman Bernstein]

In your OP you stated a desire to avoid a haul. But since you brought replacement up,those groco seacocks have a square hole on the handle so thay can be turned by placing a rachet handle in the hole to extend your reach. Its also easy enough to bolt a length of metal rod to the handle in such a way that you can push and pull on the rod to open/close the valve.

Yeah, but.....

Part of the reason for the right angle on the thru-hull is because of a clearance restriction where the thru-hull is placed, so I don't think I can get away from the right angle, regardless. Besides, I'd then need a right angle double barb fitting, plus more 2" ID sanitary hose, to be able to make it to the thru-hull. All other things being equal, more fittings = more opportunities for failure. Also, the top quality 2" sanitary hose that is used in the boat can't really be described as 'flexible', by anyone other than Superman.... it's incredibly stiff, and I'd have a hell of a time trying to bend it outwards to mate up with a different thru-hull configuration. Jenneau builds a really excellent boat, and I don't think (especially considering the price) that they went with the existing arrangement in order to 'cheap out'... there's no evidence that they did this anyehere else on the boat, whose fit, finish, and standard equipment is universally of outstanding quality.

Also, moving the thru hull can't be done while hanging in the slings... I'd have to haul and block, which is even more expensive.

[Paul G.]

I would determine the metals involved, if the hull fitting is bronze I would get a bronze valve. Then to replace the valve I would plug the hole from the outside with a plug gently tapped in or even a small bit of ply temporarily gooped on as its only .25 psi at that depth, so dont worry about the water.

[Norman Bernstein]

Well, I just got off the phone with John Cly, who is a tech guy from Groco, who gave me a great deal of information... I have to congratulate Groco on customer service, he was fantastic, answered every question, provided advice, etc.

First, on the issue of the thread spec: he doesn't know who 'MT Full Flow' is either, and he's not absolutely certain that the threading of the valve I have is actually NPT or some metric spec... but suggested that I stop and pick up a 2" npt male fitting of some kind, and test the open end.... if it fits, then he's certain the other end will be the same.

Next, with regard to the suitability of stainless steel for a sewage application: they sell the same valve in two different material setups: totally stainless (body, ball, and handle), or cast bronze with a chrome plated bronze ball. The bronze/chrome plated bronze valve is less expensive. He claims that they've had no problems whatsoever with either material combination when used in sewage applications.

As for replacement, he recommends teflon paste, rather than teflon tape. His argument is that teflon tape is a thread lubricant, not a sealant... but teflon paste serves both functions.

Finally, with regard to in-water replacement, he concurs with careening the boat, but also suggests that a soft tennis ball, slathered with some goop, can be crushed into the hole. I think I'd go with the tapered plug, though.

I'll see if I can't snap some photos tonite with my iPhone and post them.

[Todd D]

Just use the rubber part of a plunger over the thru-hull on the outside. Waterpressure will keep it in place. If it is a bronze thru-hull then put a bronze valve on it. Personally I would haul the boat and install a proper bronze seacock.

[boattruck]

Gents, A haulout is a very good idea, especially considering the unorthodox nature of the plumbing to be replaced, the chances of a good serviceable installation while green water fire hose is busy trying to sink your boat are low. Additionally, all of the parts in this daisy chain of plumbing should be checked and replaced as needed, a process that takes a little time, time that you will not likely have if you go at this like a Chinese fire drill ...The likely outcome if this sort of adventure is that you will end up limping into your boatyard with a hasty, leaking patch, begging them to haul you soon, and will end up spending all or more than you would if you just went at this chore in earnest and workman like manner from the get-go. Best wishes, BT

[Tumzara]

This post has been running for about 8 hrs now on what should be at worst a 2 hr job.
Heel her over and change the valve.
Could have had a 5hr sail as well.

[C. Ross]

Where is the ball valve relative to the water line?

I'll bet since there's no seacock, it's above the WL and safe to change in a leisurely fashion.

Those French is awful clever.

[ramillett]

I replaced the copper water tanks on my boat , and while doing that I added a 40 gallon stainless holding tank . The guy who built the tanks talked me into twice the thickness on the holding tank ( really wanted me to go plastic ). Even with that in less than 10 years we started smelling things , Unfortunately he added baffles that retained the solids , so it was all we could do to get it out of the bilge . The top of the tank had a bunch of pin holes . The only good thing was the turn around time . I dropped the old holding tank at the rotary molder's on Monday , with a quote to have parts in two weeks . On Wednesday I get a phone call asking if they could PLEASE through the old tank in trash , it was stinking out the how shop , and your parts are done I'm not big on stainless and sewage , If it were me I would go all bonze fittings , with delrin , or teflon ball if you can find it , it will last for ever

[Norman Bernstein]

Where is the ball valve relative to the water line?
I'll bet since there's no seacock, it's above the WL and safe to change in a leisurely fashion.

Nope, the thru-hull is about 4" below the waterline, when the boat is level. On the rare occasions where we actually use the valve to drain the holding tank (WELL offshore), we try to do it on a starboard tack, so the outlet is further below the waterline.

Those French is awful clever.

They build a terrific boat. Admittedly, there are a few minor quirks, but for the most part, it all works amazingly well, and it's got superb fit and finish. Unlike previous boats, this one has an excellent manual with a full schematic for all wiring and plumbing... unfortunately, no manufacturer info on the plumbing parts, though.

I replaced the copper water tanks on my boat , and while doing that I added a 40 gallon stainless holding tank . The guy who built the tanks talked me into twice the thickness on the holding tank ( really wanted me to go plastic ). Even with that in less than 10 years we started smelling things , Unfortunately he added baffles that retained the solids , so it was all we could do to get it out of the bilge . The top of the tank had a bunch of pin holes . The only good thing was the turn around time . I dropped the old holding tank at the rotary molder's on Monday , with a quote to have parts in two weeks . On Wednesday I get a phone call asking if they could PLEASE through the old tank in trash , it was stinking out the how shop , and your parts are done I'm not big on stainless and sewage , If it were me I would go all bonze fittings , with delrin , or teflon ball if you can find it , it will last for ever

I agree. When I bought the boat, one of my greatest concern was the fact that they used stainless holding tanks... but they assured me that the tanks had an internal coating. I would have preferred plastic tanks, although from previous experience, odors do permeate through the walls of a plastic tank... the stainless ones are completely odor-free.

As for the replacement ball valve, I'm going to go with the bronze version, with the chrome-plated bronze ball. I can feel the inside surface of the existing stainless one, and it's definately corroded.

[James McMullen]

On the rare occasions that we use it. . .

Seems to me that you could avoid any chance of Murphy showing up and wait until you're hauled out then. Why borrow extra trouble? Why not just pump it out at the dock like usual until you're going to haul anyways and change it then? Or is the valve corroded to the point where you're expecting a risk of catastrophic failure and you gotta change it quick?

[BrianW]

First, on the issue of the thread spec: he doesn't know who 'MT Full Flow' is either...

Geez, that's easy.

Surprised nobody has mentioned it yet. "MT" is the abbreviation for "empty", as in "empty" your holding tank. "Full Flow" means, don't just crack it a little bit, open it all the way for "full flow" or the turds will never make it out.

Sorry Norman, I just had to participate with ya above decks. This was the best I could do.

[ILikeRust]

A "full flow" ball valve is one in which the hole through the ball is the same diameter as the inlet and outlet pipe diameters. I.e., the ball itself does not offer a restriction. Your average hardware-store ball valve typically has a smaller hole through the ball, so the ball valve reduces the flow in the line even when fully open.

[ILikeRust]

I'm thinking "MT" refers to the threads - either "male thread" (is it so equipped?) or referring to some threading specification or standard (such as NPT, etc., but perhaps a metric or European standard?).

Kinda guessing at that...

[Norman Bernstein]

Sorry Norman, I just had to participate with ya above decks. This was the best I could do.

Hmmm... pretty lame, but I DO appreciate the effort