Drain Water Heat Recovery
I’d read very little about drain water heat recovery (DWHR) systems prior to this weekend, but after seeing it referenced in some Energy Star documentation I decided to look into a little further.
Put simply, a DWHR unit captures heat from your waste drain water and redirects it back into system. It’s estimated that it can recycle up to 60% of the wasted heat, save up to 40% on water heating costs, and reduce your home’s overall energy consumption by 5-10%. It would be entirely cliched to say it’s saving money from going down the drain, but that’s more or less what it’s doing.
The technology is actually quite simple, and I must admit that I’m surprised it’s not mandated on all new home construction. A portion of the main-stack drainpipe is removed and replaced with the DWHR unit. The unit itself is simply a large copper drainpipe wrapped with a series of smaller copper tubes. The smaller tubes are connected to the cold-water supply, and the water running through them will see a temperature increase of up to 14°. This decreases fuel consumption simply because it requires less energy to heat the warmer water. Similarly, it works incredibly well with tankless hot water systems, which are known to perform poorly when the groundwater is overly cold.
I don’t believe there are many drawbacks with such a setup, although I’ve read claims that water pressure will drop once the device is installed. Apparently the “second generation” units present no noticeable drop in pressure, and I doubt they’ll have an affect on the PEX manifold system we’re considering.
From what I can gather, there are 3 different models available in Canada:
The systems all look more or less the same, although there are a few key differences. The Power-Pipe appears to have more transfer tubes running in parallel, which I believe helps maintain pressure. The LC-GFX site actually scares me a little, and I couldn’t help but notice the conspiracy propaganda that litters it (stolen trade secrets, Energy Star hoaxes, and fraudulent tests?!). That said, it is significantly cheaper… although one has to wonder why (I picture an angry old man, bitter at the world, building these things in his basement).
Prices seems to range from $400 - $1200+, but they qualify for up to $260 in government rebates. To qualify for a rebates, the DWHR unit must be at least 30% efficient (43% for the maximum rebate), and to qualify for the Energy Star certification, it must be a minimum 48″ in length.
Post Tags: eco, energy, heat recovery, hot water, savings
I’m really surprised that I haven’t heard of this! See of you can get a better deal for 2. I’d consider this and a tankless combined.
A
— posted on August 31, 2008Love your site , I’ve been wanting to either buy buy or build a green home as well. what I’ve seen seen is solar panels, that heat water. Have you researched this as well and how do they
compare or can both be used.
Thanks in advance
— posted on September 2, 2008Thanks Andrew,
Indeed, we have looked into the solar heated systems… however, we decided against them mainly because they typically don’t produce enough hot water for a full family. You’d need the solar setup + a storage tank + another heating source (be it a traditional tank, or tankless). I was wasn’t too thrilled about the aesthetics of the units either. You end up with this ugly tank and array up on your roof, which wasn’t appealing at all. There are other systems that keep the tank inside the house, but for the cost and simplicity, I figured we’d be better off to just go tankless.
All that said, a DWHR unit can be used with ANY domestic hot water system. It’ll work with solar, tank or tankless.
— posted on September 2, 2008There’s another Canadian manufacturer too: http://web.mac.com/winstonwork.....nergy.html
He makes heat recovery systems that work with intermittent devices such as dishwashers and washing machines.
Paul.
— posted on September 2, 2008Hi!
As per http://oee.nrcan.gc.ca/residen.....-grant.cfm the minimum efficiency needed for federal rebate is 30% (for over 43% you get more money back). There is no requirement for the length.
The Ontario rebate is based indeed on length, and starts at 75 cm.
Am I missing anything?
— posted on September 2, 2008Vasile
Hey Vasile - good catch… I’m going to update the post to reflect these clarifications.
You’re definitely correct about the efficiency; 30% is the minimum. The length requirement is actually stipulated in the Energy Star requirements, under Table 3.12.1 “Fuel Savings Credits”.
The Energy Star documentation can be found here: http://www.360winnett.com/wp-c.....202007.pdf
— posted on September 2, 2008Hi there!
I just found your site through the Star article. Thought you might be interested. My husband and I just finished doing our own green build also in Toronto (Birchcliffe/Beaches area). Just moved in at the beginning of August. You can take a look at the blog if you want to see some of the issues we encountered. (many many many!!) The house has everything from passive solar and cooling to infloor heating, super insulation, solar panels and next year we will likely be installing the green roof.
We actually installed two Powerpipes in the basement. The technology is really very interesting not to mention Canadian. I don’t know the overall effect on the water heating yet (still too new) but it doesn’t affect our pressure at all!
Good luck with your project! Just remember, if something can go wrong, trust us, it will!
— posted on September 8, 2008Hi Donna, Thanks for sharing the link - I’ll definitely check it out.
— posted on September 9, 2008Another Canadian Manufacturer is Watercycles. http://www.watercycles.ca
— posted on September 29, 2008Can you add the link to Donna’s blog in her Sept 8 comment about their building experiences?
— posted on October 13, 2008Hi Joel - here’s the link she was referencing:
— posted on October 13, 2008http://leda.elemental-net.ca/blogs/pensivemonk/