View Full Version : Bilge pump questions

03-30-2015, 11:24 AM
I've got three old bilge pumps. (39' Concordia Yawl). I kinda don't see the need for three. I was thinking of doing two and put one at the lowest point and the second somewhat higher up.

How much higher up on the second one do you think? And what capacity? Anything else to think about?

Ian McColgin
03-30-2015, 11:40 AM
You should have at least three, especially if two are electric.

A very standard installation is to have a 1-1/2" or 2" diaphram pump for emergency. These are so rarely used that you need to remember to put changing the diaphram and check valves regularly or it just won't work when you need it.

On the the electrics. I hate them as too often they lead to the boat owner not knowing what's happening. But I live aboard and it's easy to stay up with the bilge - easier on the boat than here. So, for the electrics and assuming, as with most boats, that there's one place where all bilge water ends up:

Smaller capacity pump low as possible. It will be pulling out the routine water and won't work too hard. Small both to save battery and to keep too much water from just being stored in the hose.

Large capacity with it's strum box a bit higher. This is the pump that comes in when you're getting rid of lots of water at once, like you've just staggered up from a knock-down and a few hundred gallons got past the barge boards and cockpit locker lids.

All pumps should have at least one check valve as low as the hose goes. Nothing worse than a little too much water due to flat batteries and negligence leading to the pump discharge seacock going under and, despite the vented loop you should also have, back siphoning your way to the bottom.

On at least the smaller pump and possible the larger have a counter. This just clicks on a count when the pump goes on. For routine leakage on the smaller pump, the amount of water pumped each cycle is so close to the same that that's all you need to know.

Tristan Jones once wrote that wooden boats don't sink all that often . . . because they carry so many pumps. Do likewise.


03-30-2015, 12:01 PM
I forgot the manual pump. Yes, there is one already. I do need to see if it works.

Thanks Ian for the tips. It all makes sense. Right now, the pumps dump into the cockpit and thence down the cockpit drains. I'm going to add a thru hull for the lower one and the upper will stay in the cockpit so I can be sure to know when it comes on and no issues about siphoning.

03-30-2015, 12:07 PM
How much higher on the second bigger pump do you think?

ron ll
03-30-2015, 12:46 PM
One of the best things I installed on my boat was a bilge pump counter. It is wired to a little digital readout in the pilot house and tells me how many times the primary bilge pump has turned on since the readout was last reset. It tells me many things about the condition of my boat. By watching it over time, I learned that my hull was not leaking at ALL. The only times it would count was after a heavy rain which lead me to finding and fixing some deck leaks. It will also tell me how my stuffing box is working while running. Another time I noticed that my bilge was pumping but it was not registering on the counter. Which lead me to discover that the secondary pump was pumping and the primary was broken. The counter was cheap, took a little work to run a couple of extra wires, but WELL worth it. Here is the one I have:


03-30-2015, 01:06 PM
If you go with the one pumping into the cockpit, have it a good way above the primary pump (I'd guess 4"). Pump that empty into the cockpit easily trigger seasickness. I''ve never sailed with a bilge pump counter buut have heard good things about them, of course if the pump runs continuously the counter will show 1. Make sure there's an LED on the primary pump..

There was a superlative article in Professional Boatbuilder a few months ago, it was by Steve D'Antonio. Maybe Scot or Carl could help you reference it (couldn't find a search button).

03-30-2015, 03:21 PM
Wire both to the battery?

I currently have one that goes through the distribution panel. I thought you always go to the battery and have an in-line fuse?

03-31-2015, 11:10 AM
I have two electric. As Ian mentioned, I put my smaller pump at the lowest point and have it connected to my large house battery. It has a small diameter hose and is great for keeping up with rain, a large wave, etc. Since it is wired to my house battery (directly with in-line fuse) it will run for a loooonnnnngggg time. My larger pump is what I consider my emergency and backup. I do have it higher, but I don't know how much higher. I know that it has never kicked on because of water level rising above the level the primary pump can take care of. It is positioned in more of a "where will it fit properly" vs. "how much higher do I want it". It is connected to a separate battery (the starting battery - not ideal, but that's what I've got).

My logic is: my primary pump will keep up with everything I should expect to have happen except a dead house battery or damage to the vessel. If the battery dies, then the backup pump should take care of routine rain, etc even though it's on a smaller battery. I check the bilge frequently and I'll know by the water level if the primary is not working, so I don't expect the back up to have to be in service for long periods of time. HOWEVER, if I have damage and the primary is overwhelmed, I'm assuming I will be on board and running the engine which should keep my battery topped off enough to fend off the rising water while I make repairs. If I'm not on board, it's very likely that any pump on any battery is just buying a finite amount of time to discover the problem.

Probably not the best solution, but provides primary and alternate with different capacities and connected to different power sources (both directly connected to the battery). I too have a manual backup which of course can be connected directly to me with an in-line fuse.