Gray-water for toilet?

[conradpdx]

Don't know if the heat exchanger would work real well with such small amounts of water. Yes, there is a lot of heat lost to used wash water, but really by the time you include the air exposure from use, settling in the typically cold tub, flowing through the drain, heat lost to the pipes I doubt the typical shower would be enough to justify the cost of making the exchanger considering the amount of heat needed to keep your water heater full. Now if you were a laundry or someplace that used 100's of gallons a day the exchanger might be worth while.

However, not to get off topic, for preheating well water or even municipal water supplies a solar water heater is quite easy to build and install for most fairly competent DIY'rs. It's quite easy to google plans for one (I like Mother earth news personally). This is one of my projects for this next spring.

[bennelson]

I have poor solar access, so a DIY solar water preheater wouldn't do me much good. (Although they ARE great return on investment AND very practical overall.)

I was just thinking of a very basic heat exchanger. Something easy and cheap - one pipe inside another, something like that.

Even if waste water was temporarily held inside the house, I would get some heat just from the water in the tank radiating it's heat out.

I know it wouldn't be a big thing, but I was just thinking that if I can get some of the heat back, why not?.

[rmay635703]

Originally Posted by Sandy

It's a great idea,
but the gray water could make the bowl look less that clean,
and if you're married to a clean freak (like some one I know well)
it could be an issue.

This is actually quite simple to avoid, DONT filter the stuff, use it to flush and after the flush down is complete have the refill of the bowl occur with fresh water.

In this way the majority of the water would be gray water but the pretty appearance of clear water could be maintained.

I have thought that this idea should have been implimented long ago, that or composting toilets getting around the water issue altogether.

If people would use greener cleaners and not put crap in the toilet that doesn't belong all grey water could be shunted to be used for watering lawns and whatnot.

[Ryland]

Originally Posted by bennelson

It might be possible to design a heat exchanger as part of this system so that incoming (cold) well water could get pre-heated before going to the water heater.

you can get a heat exchanger that goes on the drain, it's a short run of 4" cooper drain pipe with 1/2" copper wrapping around the outside, leaving the inside of the drain pipe smooth to prevent clogs, in my mind the best way to make use of this otherwise lost heat would be to have your newly heated heat your cold water that is going to your shower valve so the run of pipes would be rather short, so once your drain water heats up it starts to heat up your cold water coming to the shower head, letting you turn down your hot water valve, so you pull less water from your hot water heater, get a thermostatically controlled shower valve and it will adjust automatically to keep your shower water at 130F or whatever you set it at.

[extragoode]

This is a little off topic, but I saw a waterless urinal while I was out in California. I don't know how it works or what the difference is, but I thought it was worth mentioning if your ultimate goal is to save water.

[bennelson]

I am not particularly interested in "alternative toilets" right now.

I did read HUMANURE a while back. It is a very interesting book and worth reading.

My main concern is with the amount of waste-water from the shower and washer, and the concept of simply re-using it, instead of running it out to the blackwater tank right away.

We could have an entire 'nuther thread on all the different ways to save water, but I thought the washer/shower to toilet idea is an interesting possibility.