A visit with David Velan of Ecodrain: drainwater heat recovery comes of age

Today David Velan of Ecodrain paid us a visit here at South Mountain so my colleague Brice Delhougne and I could see his product firsthand. A few years ago David got interested in capturing the waste heat in shower water and other hot waste water. Others have done that (Powerpipe) but they have been limited to applications where the vertical heat exchanger, usually 4-6 feet long, can fit, and still be higher than the wastewater outlet from the building. Ecodrain's innovation is a wastewater heat exchanger that can be mounted horizontally.

In the photo below, you can see the inlet and outlet, which is 2 inch PVC, and the side taps for the inlet and outlet for the potable water. The unit is about 56 inches long. The flow is countercurrent - the wastewater on top flows one way, and the potable water below flows in the opposite direction and picks up heat across the copper interface. Depending on the relative flow rates, and the pitch of the unit, the Ecodrain recovers 30-45% of the energy in the wastewater.

David went through many evolutions before arriving at his product. It has a double wall heat exchanger configuration that should satisfy codes (the product has a UPC acceptance) and square section tubes on the potable water side to maximize heat exchange contact area. The upper portion of the unit is PVC and is smooth to minimize any buildup of solids. Here's a cross section:

One of the Ecodrain innovations is seen in each square tube - it's a plastic insert designed to keep the flow highly turbulent to increase heat transfer.

The bottom of the unit has a drain hole so that any leaks become obvious quickly.

The unit is designed to work with very slight pitch, like a typical plumbing waste line, but it can be pitched at more severe slopes, and the increased velocity of the wastewater increases heat recovery.

The unit can be plumbed so that the preheated water flows to the cold side of the shower, or to both the shower and the cold inlet of the water heater. The latter equal flow configuration will harvest the most BTUs.

Let's do some Marc's Sloppy Math. Say a family uses 30 gallons/day of shower water and 1/3 of that energy is recovered. That's about 625 kWh/year. At $0.20/kWh (MA residents are about to see a 30-35% rise in the supply portion of their electric bills due to last winter's natural gas price squeeze!) that's $125/year. The unit costs $440, and let's say it ends up at an installed cost of $1,000. There's a simple 8 year payback. With natural gas this will be worse. To get 625 kWh/year from PV would take about 500W of panel, which costs more than the Ecodrain installed.

One application David related to me is using the Ecodrain in cases where people are running out of hot water. Recovering drainwater heat effectively stretches the storage capacity of a water heater.

David kindly left us with one and we're looking for a good application, so we can monitor its performance in an actual situation. We were impressed with the iterative thoughtful engineering embodied in the product, it's rugged construction, and the testing Ecodrain has done to show energy recovered and its clog-free performance.

Comments

[David Fay]

Marc said: "MA residents are about to see a 30-35% rise in the supply portion of their electric bills due to last winter's natural gas price squeeze!"

Actually, for National Grid customers, the supply portion just increased by 100% (8.277 cents to 16.273 cents): https://www.nationalgridus.com/masselectric/non_html/MA_Residential_Table.pdf

It's the average total bill (combined supply and delivery) that increases by 37%. Other MA electric companies will soon follow with their own increases.

[David Fay]

Marc said: "The unit costs $440"

Actually, that's Canadian dollars. In American dollars, the price is $389. That doesn't make much difference unless you do the installation yourself.

[Kate Stephenson]

Happy to install and test for you! I think I have an easily accessible shower drain. But I am wondering about the application of this technology for a commercial kitchen application with 3 bay sink and commercial dishwasher at Yestermorrow. Now THAT uses a lot of hot water.

[Marc Rosenbaum]

The Ecodrain should work well on any hot water fixture that has simultaneous drain water and hot water draw. So, not bathtubs and washing machines, for example.

[Dana]

In MA you'd need a variance to install an EcoDrain version, since it's not on the pre-approved list of plumbing fixutures for potable plumbing.

SFAIK only the only listed drainwater recovery series that wouldn't require a variance are Renewability PowerPipe series and EcoInnovation's ThermoDrain series. But being gravity-film types they only work efficiently when mounted vertically.

http://license.reg.state.ma.us/pubLic/pl_products/pb_search.asp?type=P&manufacturer=EcoInnovation+Technologies+Inc&stype=spec&model=&product=&description=&psize=50

http://license.reg.state.ma.us/pubLic/pl_products/pb_search.asp?type=P&manufacturer=Renewability+Energy+Inc.&stype=spec&model=&product=&description=&psize=50

It would be an easier sell if they were to jump through whatever documentation loops necessary to get the EcoDrain listed, avoiding the permitting & inspection headache.

What David Fay said about the winter-rates for Nat'l Grid- it's a 100% uptick on the supply portion, a 37% uptick on the total, which puts the residential retail rate at about 24-25 cents/kwh, about 16-17 cents of which is the supply.

At 16 cents it's possible to beat that by switching suppliers. It's possible buy 100% renewables from some of the power resellers (who buy long term power purchase agreements from various generators,as well as buying up SRECs and other renewable credits in various markets.) I locked in at 12 cents/kwh for 3 years from one of those.

At 16 cents/kwh it's also well over what a even rooftop solar PV lease deal would cost you. A PV purchase would be even better than a lease for the creditworthy, especially in states (like MA) where Solar City will be offering 30 year money at 4% (and a 30 year guarantee!) for the purchase of their systems. They will soon have competition, count on it! At 4% interest, even without the 30% income tax credit, rooftop PV would come in well under the 24 cents/kwh, or even the 16 cent energy-only portion!

[Eric]

Hm, David, the website says $439.95 USD. Anyway; less expensive than even the smaller power pipes. I'll have to look at the claimed BTU recovery of each. Seems like it has more PVC and less copper overall, which makes economic sense to me. I wish this had been available when we did our renovation; I may still see if I can fit one in somewhere. Thanks for the post!

[Marc Rosenbaum]

Thanks David for your clarifications, I'm having some issues with Typepad in responding to comments.