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View Full Version : Saving water - the ahaa moment - why didn't I think of this when I built my house???



Larks
08-25-2010, 04:11 AM
Here's an idea (that I wish someone had suggested to me) if you're planning a new house and need (or want) to save water.

I built my own house a few years ago, on a small rural block (2 acres) with town power but no other town services - so I have my own 10,000 gallon underground rain water tank and we are on our own sewage waste system.

When I built, I asked around for advice on water saving ideas so that I could set up our plumbing to be as efficient as possible.

The most popular idea was to set up the hot water supply throughout the house on a loop - after the hot water system - with a circulation pump on a timer so that hot water would circulate throughout the hot water line for a short period (before shower time or wash up time) to rid the line of the cold water that would otherwise be run down the drain while waiting for the hot water to come through.

Another option was to fit a small under sink water heater that gives instant hot water but only operates until it senses the hot water come through from the main water heater. That's OK for the sink but not for all of the bathrooms.

Unfortunately, at the time that we plumbed the house, the plumber that we used talked us out of setting up the loop system and ever since then I have regretted it as we loose approximately 9 litres (or about 2 1/2 gallons) of water down the drain in our shower waiting for hot water.

So at this time of year when rain is a little scarce, the water coming out of the tank icy cold, the level of that water getting quite low in the tank and the cost of trucking in 2500 gallons of water about $200.00, I get very antsy about how much water we are wasting and find myself trying to find a way of resolving this wastage without having to replumb the whole house.

And it came to me in the shower this evening.

The simplest idea of all and I don't know why the hell someone didn't suggest it when I was building the house or why I didn't think of it myself.

There are so many houses in Oz on tank water that this is just so obvious, even for houses on town water but with rainwater tanks for their gardens.

I had always been aware that the smartest thing would simply be to run the water that we are wasting back into the tank, but other than running it into a bucket and then tipping it back down our gutters to run back into the tank, I hadn't thought much further.

So why not pipe it back into the tank directly from the hot water line?

Instead of setting up a hot water loop and dedicated circulation pump, simply adding what is essentially an extra hot water tap at the end of the line with a line back to the tank would do the job.

But to take it step further, instead of stopping the hot water line at the last tap at the end of the run as you'd normally do, continue the hot water line back to the tank (or if you're on mains water, back to a tank for your garden) with an in-line tap at a convenient point in the bathroom and maybe a thermometer on the line where it can be seen.

Instead of running the cold water down the drain, turn on the in-line tap until hot water runs through knowing that the water is just going straight back to the tank.

Simple eh????

If you're wondering why I've bothered to post it here??? Well, as I said I wish I'd thought of it earlier or at least picked up the idea from someone else, so if by posting it here someone somewhere finds it useful, it'd be worth the effort.

skuthorp
08-25-2010, 04:21 AM
We put in an undersink instant heater but it has a small capacity so the pump surges, and the unit did not like this and has, I think, failed. There is only cold line to the sink, so We will install a plug in 10 litre storage heater instead. We got most things right though. Your idea is a good one I think.

The Bigfella
08-25-2010, 04:27 AM
And it came to me in the shower this evening


If you shower with a friend, you'll save lots of water and I'll bet that a lot more ideas will come to you in the shower.

skuthorp
08-25-2010, 04:34 AM
If you shower with a friend, you'll save lots of water and I'll bet that a lot more ideas will come to you in the shower.

Not necessarily Ian, it can lead to looooong hot showers mate. (Ah yes, those were the days)

JayInOz
08-25-2010, 04:41 AM
I have fifteen thousand gallons of rainwater. Also a bore which pumps almost two thousand gallons an hour into a three thousand gallon tank, with a high pressure pump on it which is capable of running eight taps at once. I also have a petrol generator capable of running the pumps in the event of a power failure. A lot of people want to defend their homes in a bush fire, but as soon as the power goes, they lose their water supply too. We put our hot water system outside, just through the wall from the shower, so the hot water arrives almost instantly. I suggested that we could save a lot of water by not showering at all- the wife suggested that I sleep outside and never visit the happy place again, so scrap that :D JayInOz

skuthorp
08-25-2010, 04:50 AM
It's not the high flow rate that's the problem, it's when the flow is small that the pump surges. We have a diesel back-up pump, but our ground water is too highly mineralised for the good of a pump. Like your place, the hot shower water arrives instantly but the kitchen is at the other end of the house. Not a clever design idea but it was difficult to change seeing we had bought a part built house.

MiddleAgesMan
08-25-2010, 05:59 AM
We have inexpensive water plus lots of rain here. But I like the idea of sending rain water to a tank to reduce the amount of water you have to buy. I'm not sure our building code would allow us to pump tank water through our houses, though. I'll have to look into that.

When I added a new master bath I installed a high capacity on-demand gas heater on the wall outside the bathroom. It could handle the shower even while filling the tub and running the sink. Unfortunately it broke down right after the five year warranty ran out and now I have to decide whether to replace it with a similar unit or tap into the traditional tank heater that handles the rest of the house.

Paul Fitzgerald
08-25-2010, 06:08 AM
We are currently planning for a house completely on tanks.

We plan to use flash heaters for shower and sinks.

Had them at work, they were great. You set the temperature so there is no wasting mixing temperature, and hot water is instantaneous.

And the house plumbing is all cold water, no need for a hot system.

I am also working on a recirculating shower system, using a sump and a flash heater, so we can still have long hot showers.....

Now if anyone has the gen on waste systems, i'm interested.

PeterSibley
08-25-2010, 06:44 AM
In the cabin I am (supposedly ) building I'm putting a very small 25 litre electric hot water cylinder about 3 m from the shower .... that should be about .34 litre of water hot water per shower .I've got plenty of water , but I don't like wasting HOT water .

PeterSibley
08-25-2010, 06:46 AM
Toilet waste Paul ? Composting toilets ?

Bruce Hooke
08-25-2010, 08:50 AM
That's an interesting idea, Larks. What I like about it is that it does not involve the very energy-inefficient practice of continuously circulating hot water. Inevitably, hot water circulating through pipes would loose much more heat that water sitting in a tank so keeping the water warm would take more energy*. Your solution gets around that. The challenge of your idea is how to engineer it. I suppose it would not be that hard to set up a system where you throw a diverter valve before turning on the water, and by that means send the cold water to a garden-water storage container, but if you are going to get into storing water for garden use, why not set up a gray-water system so you can also use the used shower water? If you want to send the water back to the hot water tank then it seems like some sort of pump would also be necessary, at which point you are talking about both throwing a diverter valve and turning on a pump, and then turning both off when you have somehow determined that the hot water has reached the shower (how would you know?). All of that is doable but it becomes a "funky" system that you have to teach any guests how to use and that would likely be an issue if you want to sell the house. The most streamlined solution I can think of is to put in the continuous loop hot water system but only turn it on when you are about to take a shower (or otherwise need hot water) and otherwise leave it off. If people tend to be pretty consistent about when they take showers in your house you could even put it on a timer.

*In many parts of the world, a major environmental cost of water usage is the energy used to pump the water from the source to the point of use. So, a system that saves water but uses more energy to heat the water is of dubious benefit in the grand scheme of things. Of course in areas where water is very limited the extra energy for heating water may be worthwhile, especially if that energy can come from a renewable source.

Canoeyawl
08-25-2010, 09:22 AM
Bruce is on to it. But I think it could be pretty simple.
You will need a pressure differential to get the system working. (Tank pressure must be lower than the feed pressure)
A small pump with a timed switch located near the shower should do it.

ron ll
08-25-2010, 10:59 AM
I have a similar problem on a much smaller scale on my boat. I carry 80 gallons of fresh water. We have a shower on board and it probably uses less water to take a shower than what is wasted waiting for it to get hot. Usually I capture it in a container and use it for engine coolant, washing salt off of pilot house windows or whatever. But I've often thought that by adding a diverter valve and only one extra hose back to the tank, this could be solved.

Another related problem is that when at anchor, the HWT is no longer heating water but just storing it. When water is drawn off at the tap, all the cold water in the hose prior to hot water arriving is replaced in the tank by new cold water, thereby diluting the temperature of the hot water stored in the tank.

BarnacleGrim
08-25-2010, 11:32 AM
Living in the wettest part of Sweden, water consumption isn't an issue, but heat consumption is. Why not insulate those hot water pipes?

Brian Palmer
08-25-2010, 11:36 AM
Waterless urinals.

Bruce Hooke
08-25-2010, 12:17 PM
A small pump with a timed switch located near the shower should do it.

It took me a minute to realize that you probably mean one of those switches that you turn to have something run for a certain period of time. If that is what you mean then that does sounds like a good solution. With a bit of experimentation you could figure out how long to set it for to get hot water to the shower. I suppose the even more elegant solution would be to have a simple on-off switch that would run the pump for a predetermined period of time, but that would take more work to engineer since it is not something you can buy off the shelf from a building supply store.

Bruce Hooke
08-25-2010, 12:18 PM
Why not insulate those hot water pipes?

I'd hope that would be a given! However, my experience has been that even with insulation around the pipes it does not take that long for the water inside to cool off.

Larks
08-25-2010, 04:03 PM
Bruce, canoeyawl, what you are talking about is really the more complex system that was originally suggested to me but which the plumber (annoyingly) talked me out of, a timed circulation pump that circulates through the line to fill it with hot water, ie an additional pump to the one that I have on my tank that simply circulates the water through the line. The commercial ones that are available have both a timer and an override switch so that in the morning if you're up before the timer goes on you can hit the switch while you're cleaning your teeth or going to the loo so that by the time you're ready for your shower the water in the line is warm.

What I'm talking about though, which I think I could possibly still retrofit because my house is up on poles, is to simply run the water that I'd normally run down the drain, straight back to my main supply tank by extending the hot water line from the last tap back to the tank with an in line tap/valve. The beauty of this is that it is just a tap and a bit more line - no additional pump or timer or thermostat or anything complex and it just runs of the house supply pump.

The other thing that I didn't mention, but which has also turned out to be a mistake, was to go with the suggestion to fit the hot water system, which is a Rinnai gas instant hot water system, centraly to all of the bathrooms, laundry and kitchen. It might seem like the logical thing to do but as a result the laundry and the guest bathroom get quick hot water, but the kitchen and our bathroom, which get the most use, have the longest delays for hot water. It would have been smarter in hindsight to fit the system closer to either the kitchen or our bathroom (which are at opposite ends of the house).




I'd hope that would be a given! However, my experience has been that even with insulation around the pipes it does not take that long for the water inside to cool off.


You'd hope so wouldn't you!!! However the plumber tried to tell me that because he had used the PVC pipe and fittings instead of copper it didn't need lagging (insulation). Fortunately here in Oz, as well as being plumbed by a licenced plumber, the plumbing has to be certified by an independant certifier and I was able to get his weight behind adding the lagging - albeit they then only did it to the exposed pipework under the house to the kitchen. I then had to go back and lag the hot water pipework to the bathrooms myself.

One very interesting thing that I see used in the States that I haven't seen to be as popular here is the spray in foam insulation that is sprayed between all frames encapsulating all of the pipework, I gather it is similar to the expandafoam that we get in cans. I have wondered about its efficiency and whether there might be an opening over here to set up a van to go around and provide the service to builders instead of the fibreglass or wool batts that we mostly use here.
http://www.insulfoamsolutions.com.au/Pages%20Builders/Overview.html


John, re the wastewater - we went with a Nature Flow aerated sand filter system: http://www.natureflow.com.au/budget_hstp.htm My wife is the scientist in the family and she researched quite a few systems before deciding on this one; the deciding factors being the use of the waste water for above ground irrigation; the robustness of the system in that if the power fails while we are away the system isn't going to "die"; minimal moving parts or failable parts; one service a year and probably a few more reasons that I've forgotten.

Bruce Hooke
08-25-2010, 04:38 PM
Bruce, canoeyawl, what you are talking about is really the more complex system that was originally suggested to me but which the plumber (annoyingly) talked me out of, a timed circulation pump that circulates through the line to fill it with hot water, ie an additional pump to the one that I have on my tank that simply circulates the water through the line. The commercial ones that are available have both a timer and an override switch so that in the morning if you're up before the timer goes on you can hit the switch while you're cleaning your teeth or going to the loo so that by the time you're ready for your shower the water in the line is warm.

What I'm talking about though, which I think I could possibly still retrofit because my house is up on poles, is to simply run the water that I'd normally run down the drain, straight back to my main supply tank by extending the hot water line from the last tap back to the tank with an in line tap/valve. The beauty of this is that it is just a tap and a bit more line - no additional pump or timer or thermostat or anything complex and it just runs of the house supply pump.

We were probably both thinking of a typical US plumbing system, which in a rural area would typically be set up so the water pressure is provided by a pressure tank that is filled and pressurized by a pump in the well (or for shallow wells sometimes a suction pump near the pressure tank). In this case, there is no place to which to return the cold water other than to send it back into the hot water tank, but again this would require a pump to create enough pressure to push the water back into the hot water heater.

HOWEVER, I overlooked that you have an unpressurized water storage tank, which very much changes the situation. Then you just have to find an inconspicuous place in the bathroom to put in a valve that you can open and close to regulate this flow. That sounds like a distinctly workable solution.

Larks
08-25-2010, 04:46 PM
Yes Bruce, that's pretty much it, I guess I wasn't very clear on the system we have. We don't have any mains water but an underground tank and we pump from it with a Grundfos CH-PC pump http://net.grundfos.com/doc/webnet/homeperformance/apreg/media/5883/ch-pc%20and%20ch-pt.pdf which is activated simply by turning a tap on in the house.

Bruce Hooke
08-25-2010, 05:43 PM
Yes Bruce, that's pretty much it, I guess I wasn't very clear on the system we have. We don't have any mains water but an underground tank and we pump from it with a Grundfos CH-PC pump http://net.grundfos.com/doc/webnet/homeperformance/apreg/media/5883/ch-pc%20and%20ch-pt.pdf which is activated simply by turning a tap on in the house.

Oh, you said it quite clearly in your first post :D ...it's just that I did not keep that information in my head once I got sidetracked onto the whole pumped loop idea...

Michael D. Storey
08-25-2010, 06:09 PM
Suggest you consider uses for grey water (shower water) like doing laundry, irrigation, etc

Larks
08-25-2010, 06:57 PM
Suggest you consider uses for grey water (shower water) like doing laundry, irrigation, etc

Michael, all our waste water, black and grey, goes through an aerated sand filter system and is used for irrigation.

skipper68
08-26-2010, 12:17 PM
We have the antifreeze pipe heaters here,that puts heat around the pipes so they wont freeze in the winter.Would it be possible to put this on the pipes that are on both ends,as to make the water hot when you turn it on?Very little energy use,and I believe they can be insulated also.This is just an idea off the top of my head. They have a similar system here for roofs, so no ice buildup to ruin the shingles.