The Ecodrain: How a simple, non-moving part can reduce hot water consumption by 40% • Hacker News Board

Re: The Ecodrain: How a simple, non-moving part can reduce hot water consumption by 40%

#21

Post by ars » Tue, Mar 24, 2009, 4:25 PM UTC

rationalbeaver wrote: post #16

ars wrote: post #12

This doesn't warm up the water to the heater, but rather the water going to the cold side of the mixing valve in the shower. If it takes me 5 minutes to get the stupid thing at the right temperature now, imagine what will happen when the temperature of the incoming cold water depends on the temperature of the drain water - and it's a positive feedback - the hotter the water, the hotter the incoming cold water, making…

According to their actual website, you can set it up so that it feeds the warmed water back into the water heater, rather than straight back into the shower. Apparently there are thermostatic mixing valves that would probably help with your problem as well (although I just read that in their FAQ and really don't actually know what that even means).

Of course you can feed it that way, but the plumbing would be very convoluted - up to the shower, through the machine, and back down to the heater. The loss in water pressure would be bad, and can you imagine having two showers? The plumbing would be nuts.

I know about thermostatic mixing valves, but I'd have to break the wall of the shower, and redo all the tile. But I guess if I'm putting in this device I could do it at the same time.

But all the thermostatic mixing values I know of actually work on water pressure - so if someone turns on a faucet it automatically adjusts to keep the temperature correct.

I don't know of any that actually measure the temperature of the water, which is what is needed to help this device.

If you want to do this properly you install a heat exchanger on your main sewer stack, and then route the incoming water line through it. They do exist, this concept is not new.

Re: The Ecodrain: How a simple, non-moving part can reduce hot water consumption by 40%

#22

Post by RobGR » Tue, Mar 24, 2009, 5:04 PM UTC

Avshalom wrote: post #4

patio11 wrote: post #2

It doesn't reduce water consumption, it reduces energy consumption required to heat water. Now, of course, the missing calculation is how much energy is required to make a stainless steel heat exchanger, install it, and perform maintenance. If that is more than 40% of the energy I spend on showers over the useful life of the device, then I'm not buying either a cost savings or an environmental improvement, I'm buying…

chances are the useful life time of a chunk of steel with a couple holes in it is as long as the rest of your plumbing

That's what I think too. But look at how often car radiators and air conditioner coils have to be replaced. Hopefully since this doesn't have to hold pressure, or work at very high temperatures, it should last longer than the house.

Re: The Ecodrain: How a simple, non-moving part can reduce hot water consumption by 40%

#23

Post by HeyLaughingBoy » Tue, Mar 24, 2009, 5:22 PM UTC

rationalbeaver wrote: post #18

mattmcknight wrote: post #3

This line didn't add up for me: "likely your most energy-intensive daily household activity". I think overall temperature control for my house is vastly more expensive than this, given that my gas bill drops to $45 in the summer but touches $300 in the winter. I also run the dishwasher every day and do an average of one load of laundry per day (kids!). Not a bad idea for new construction, but dialing back your hot wa…

While I pretty much agree with you, and the water heater advice is great, I suspect that a decent part of that $300 jump in the winter is because the temperature of the water entering your home during the winter is much colder than it is in the summer (a.k.a. it costs significantly more to heat the same amount of water in the winter than it does in the summer).

Probably not. Water entering the house comes in below the frost line so the pipes don't freeze in winter and the ground temperature below the frost line is pretty constant year-round. There is a small change, but the water coming out of my cold faucets is almost the same temperature whether is 100F or -25F outside.

Re: The Ecodrain: How a simple, non-moving part can reduce hot water consumption by 40%

#24

Post by shawnyar217 » Wed, Mar 25, 2009, 4:32 PM UTC

bprater wrote: post #5

Pretty brilliant in it's simplicity. I'm not sure how it'll deal with all the crap that always works it way down the drain, though.

This is from the FAQ on the EcoDrain website:

    When my drain clogs, I use chemical and/or bacterial
    cleaners to unclog it. Is it safe to use these with the
    EcoDrain?

    The EcoDrain is corrosion resistant and it is as safe to
    use chemical and bacterial cleaners with the EcoDrain
    as it is for the rest of the piping.

The FAQ also says there is a non-stick coating to help prevent buildup inside the unit.

Re: The Ecodrain: How a simple, non-moving part can reduce hot water consumption by 40%

#25

Post by whatusername » Thu, Mar 26, 2009, 12:28 AM UTC

ars wrote: post #12

This doesn't warm up the water to the heater, but rather the water going to the cold side of the mixing valve in the shower. If it takes me 5 minutes to get the stupid thing at the right temperature now, imagine what will happen when the temperature of the incoming cold water depends on the temperature of the drain water - and it's a positive feedback - the hotter the water, the hotter the incoming cold water, making…

Try living somewhere where there's a drought! We're asked to limit our showers to under 4 minutes (including getting the temp right!)