Power-Pipe, Effectiveness of drain water heat recovery systems ???

Considering installing one but not sure if the claims are accurate for effectiveness or if it's simply "snake oil".

My current shower drain is 2" but I can use an entire floor below the shower for length. So I could use an 78 or 82 inch version from Power Pipe



Claims it's 53-56% efficient?

Is it to be believed it will make a big difference?

Would it be worthwhile to insulate the power pipe and heated side of the line?

Thanks

A 60-inch Power-Pipe System, for example, can raise the cold water temperature from 10°C (50°F) to as much as 24°C (75°F), under equal flow conditions.

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It never hurts to insulate the hot lines. Not all systems are created equal, but yes, they do work. The longer the heat exchanger, the more heat it can extract. Dana has studied this a lot, I'm not up on the variations between brands. They're big in Canada since their climate makes the incoming water colder, so you use more hot to get the desired temp...warming up the cold means less hot to use. I'm not much further north, but I've measured incoming cold water at barely above freezing after a cold spell. The better ones use square tubing and split the stream into more than one to get more heat exchanger surface area.

I have now had 2 power pipes installed. One in my old house and one in the house I've just had built. I can confirm that when someone takes a shower I have placed my hand at the inlet and outlet and the temperature difference is significant. Mine were both 4". The first one was 68" and the most recent one is 72" I believe.

I know Dana is a strong proponent of the concept. I also know in plumbing you get three opinions for every two people.. lol

That's why I am asking this question in a new thread.

I would like to go with a 3" but it so very tight within the wall AND I believe by code if went to 3 inch I have to continue 3 inch to the stack. The 2 inch is glued into the only available entry into the stack. Looks like a bear to change the drain to 3 inch into the stack... and better off left as-is... Good decision?

jadnashua said:

It never hurts to insulate the hot lines. Not all systems are created equal, but yes, they do work. The longer the heat exchanger, the more heat it can extract. Dana has studied this a lot, I'm not up on the variations between brands. They're big in Canada since their climate makes the incoming water colder, so you use more hot to get the desired temp...warming up the cold means less hot to use. I'm not much further north, but I've measured incoming cold water at barely above freezing after a cold spell. The better ones use square tubing and split the stream into more than one to get more heat exchanger surface area.

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Power Pipe brand is your brand of choice I take it? Did you research it or just pick it?

Wish I had bought one a while ago before copper got so expensive and prices went up a lot!!!!

ANGELofDEBT said:

I have now had 2 power pipes installed. One in my old house and one in the house I've just had built. I can confirm that when someone takes a shower I have placed my hand at the inlet and outlet and the temperature difference is significant. Mine were both 4". The first one was 68" and the most recent one is 72" I beleive.

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What temperature is the water you shower with? Usually it is only 120 degrees, or less, and since the amount of heat transfer is DIRECTLY related to the amount of disparity between the hot and cold water, the amount of heat transfer surface, the "cleaness of the pipes interior, and the length of time for the exposure, the amount of energy saved by these devices is minimal. Some convert the 2" drain line to a series of smaller lines, giving greater wall surfaces, but introducing a greater degree of potential stoppages and difficulty unplugging them. The efficiency will drop dramatically, as the interior surface accumulates an insulation of soap and hair buildups. Personally, I would not even consider investing my money in one of the systems.

hj said:

What temperature is the water you shower with? Usually it is only 120 degrees, or less, and since the amount of heat transfer is DIRECTLY related to the amount of disparity between the hot and cold water, the amount of heat transfer surface, the "cleaness of the pipes interior, and the length of time for the exposure, the amount of energy saved by these devices is minimal. Some convert the 2" drain line to a series of smaller lines, giving greater wall surfaces, but introducing a greater degree of potential stoppages and difficulty unplugging them. The efficiency will drop dramatically, as the interior surface accumulates an insulation of soap and hair buildups. Personally, I would not even consider investing my money in one of the systems.

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The PowerPipe (and all of those I've seen) maintain the ID of the drain pipe. What does potentially get divided is the potable water lines that are wrapped around it. So, that would have no effect on potential clogging. The drain water is probably arround 100-degrees F starting down the drain. In cold weather climates, the incoming winter water temps can approach freezing, so there's a delta T of 50-70 degrees or so. Being all made of copper, the heat transfer is decent, and can warm that incoming water a fair amount, easily enough to let you lower the hot water usage. Now, whether in any one situation, it would pay for itself in a reasonable time would depend on local conditions including utility costs.

I have a tempering valve set at 120, I scootched it up a few degrees and at the beginning the shower temp control is in the middle. It's a pretty new Delta shower called a Carlisle, has their latest cartridge in it.

hj said:

What temperature is the water you shower with? Usually it is only 120 degrees, or less, and since the amount of heat transfer is DIRECTLY related to the amount of disparity between the hot and cold water, the amount of heat transfer surface, the "cleaness of the pipes interior, and the length of time for the exposure, the amount of energy saved by these devices is minimal. Some convert the 2" drain line to a series of smaller lines, giving greater wall surfaces, but introducing a greater degree of potential stoppages and difficulty unplugging them. The efficiency will drop dramatically, as the interior surface accumulates an insulation of soap and hair buildups. Personally, I would not even consider investing my money in one of the systems.

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Who's Dana Dominic?

This subject is so interesting. I would like to see how the first few installs go in and what people's opinions are. As yet I have only seen the systems online. No job site installs as yet.

My house could be a good "Geniune Pig" I'm thinking.

JW

I've been using a PowerPipe in my house for the past 2 years. You can read about it here: https://terrylove.com/forums/showthread.php?39506-Drainwater-heat-recovery-installation&highlight=

It's still performing the same as it did when I first installed it--no sign of any degradation in performance. It's still cutting my showering hot water usage in half. (Incoming water at 6C gets heated to 19C with the shower running at 40C).

In one more year, I'll be at break-even cost and then it'll be all gravy after that.

johnfrwhipple said:

Who's Dana Dominic?

This subject is so interesting. I would like to see how the first few installs go in and what people's opinions are. As yet I have only seen the systems online. No job site installs as yet.

My house could be a good "Geniune Pig" I'm thinking.

JW

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Beats me!

Even though the original patents for gravity film heat exchangers on drains were from a US inventor/company (and tested by the US D.O.E. back in the early 1980s), the bulk of the development and study since has been in Canada, where the year-round average incoming water temps are generally lower than in most US locations, and thus the benefit higher. Most of the current manufacturers are (no big surprise) Canadian, but it's still a tiny market, with a lot of infighting (backstabbling?) amongst the players with claims and counterclaims over intellectual property, safety agency mis-labeling, etc.

They have qualified for various national/provincial/local subisidy that sometimes varies by model based on the third-party tested performance to Natural Resources Canada's standard parameters.

Only recently has Ontario allowed them to be counted as part of the whole-house efficiency package for purposes of code compliance:

http://www.greenbuildingadvisor.com.../drain-water-heat-recovery-gets-boost-ontario

Industry-leader Renewability (PowerPipe) has nailed the distribution contract game in Canada, being handled by both Sears and Home Depot. In the US they use EFI, though IIRC they can also be ordered off Home Depot's US webstore. Most of the others can only be had in the US via "buy direct" manufacturer's websites.

I haven't bothered instrumenting mine, but it's clearly doing the job, since I've dialed back the output on the boiler to where it couldn't possibly keep up with a sustained shower without the input of the drainwater heat recovery unit. But with the DWHR I can shower all day with all zones calling for heat, never running out of either heat or hot water, and the output of the boiler never exceeds ~60-65,000 BTU/hr. Both the "hand on the pipes" and infra-red thermometer tests show several 10s of degrees of temperature rise through the DWHR, bringing even winter-incoming water up to above room temp, but not exactly "warm-warm", just "tepid-warm", which is about what I'd expect out of a ~50% recovery-efficiency tested unit like a 4 x 48 incher.

Whether it has any "payback" or not depends on your energy price points. For families heating hot water with electricity, propane, or oil it has a fairly high ROI, but for those people who have 50 cents/therm natural gas there's no cash argument for them, only the "apparent capacity" performance that allows multiple showers in rapid succession (or continuous low flow showers), from even the smaller-burner gas-fired tanks.

Even though I can't stand their historical (and apparently present) web-forum presence/style and would thus never buy from them myself, the buy-direct price/performance for ThermoDrain is pretty good compared to their competitor's full-retail buy-direct pricing, or the Home Depot/Sears pricing. Plumbing professionals in Canada can probably get the wholesale pricing from WaterCycles or Renewability through other channels. I'm not sure if EFI can ship direct to Canada without being in violation of their distribution contract, but I suspect that would be the case.