We continue now with our examination of the Energy Efficiency Evaluation Report we received for our house under the ecoENERGY Grant program.
According to Home Depot , this next recommendation is ‘…about 4 times more cost effective than a solar water heater’.
Unfortunately, the report did not have an explanation of what a drain water heat recovery (DWHR), so we used our favourite Internet search engine to find out. And, boy, are we glad we did.
This energy conservation device has no moving parts (we like that), consumes no energy itself (we like that even more), requires no maintenance and is sold by many vendors with multi-year (four or more) warranty.
It’s a simple concept. Hot water, say from a shower, leaves the house at around 37 degrees Celsius through a vertical drain pipe. Cold water at around 11 degrees Celsius will come into the hot water tank from the outside to replace the hot water used during the shower. This device is simply a copper drain pipe (through with the used hot water from say the shower leaves the house) with a much smaller copper pipe (through which the colder water comes into the house) wrapped around it.
As the hot used water leaves the house, it warms up the copper piping which then will warm up the incoming cold water to around 25 degrees Celsius. This means that the hot water tank no longer needs to heat the incoming water from 12 degrees to 37 degrees, but from 25 degrees to 37 degrees (Celsius). The hot water tank does less work, saving energy to heat the water.
The cost is between $600 and $800, plus sales tax at Home Depot (and possibly other big box stores), including drain connectors, plus installation cost.
We like this idea a lot because of its simplicity. The grant is only $200 (Federal / Provincial combined) vs the $400 combined grant for the tank-less water heater which costs about twice as much (hence why the larger grant for the DWHR.
What is not clear to me is can you use both together? I don’t think so, but I will follow up with the ecoENERGY Grant company and report back to you.
To continue with the next article in this series, simply select this link to Part 8.
8 responses so far ↓
1 Andre Cayer // Jan 15, 2008 at 3:36 pm
Hello,
In responnse to your question regarding the use of DWHR and tankless:
DWHR and tankless are ideally suited for each other. Since most tankless are actually designed for 21C/70F cold incoming water temp, they struggle with colder temperatures under demand. In many parts of Canada, ground water temperatures below 5C during winter months are not uncommon. Summer time ground water temperatures in any part of Canada are rarely over 15C. The benefit of DWHR is they can ensure the cold water entering the tankless system is 18C or better no matter how cold the incoming water is during a shower. I hope this is of some assistance.
2 Kate Butler // Jan 15, 2008 at 4:31 pm
Hi!
Just thought I would let you know that there are a number of other providers of Drain Water Heat Recovery Systems in Canada besdies Home Depot (which I do believe is online orders only). I am unaware of other box stores, just eligible manufacturers from whom you can order. The link for eligible providers from NRCan is http://www.oee.nrcan.gc.ca/residential/personal/retrofit-homes/questions-answers.cfm?attr=4#q35
I hope this is helpful. Good Luck with the renovations!
3 Dan // Jan 16, 2008 at 11:37 am
Hi Andre,
Your point about how a DWHR can extend the life of a conventional (for Canada) water heater as well as an instantaneous (tankless) water heater is one which I do not recall see being mentioned in the research we did. Thank you for pointing this out. We will add a post in a few days on this.
Best Regards,
Dan
4 Dan // Jan 16, 2008 at 11:39 am
Hi Kate,
Indeed. Many thanks for the link. When we go to investigate having one installed in our own home we will be sure to check out many of the suppliers in your link.
Kind Regards,
Dan
5 ToolGuy // Jan 19, 2008 at 11:29 pm
The design for DWHR seems simple enough. At a cost of $600 to $800, I would think one could make their own with some copper tubing. Making the bend without kinking the tubing might be a little tricky, but at the price of buying the unit, I would figure out a way. Also seems wraping it in insulation would be beneficial, making it more efficient. Just some thoughts.
6 100th Anniversary Edition // Feb 3, 2008 at 4:53 am
[…] ecoENERGY Report - Part 7 - Recommendations- An article about a relatively new Canadian invention to significantly reduce the amount of energy […]
7 Bill Lynn // Jul 1, 2008 at 1:57 am
The DWHR seems simple, but in my house there are a number of drains that feed into the main drain at different points
(bathroom sink drain, tub/shower drain, basement shower / sink drain, kitchen sink / dishwasher drain, laundry tub / washing machine drain).
It would seem to be a plumber’s nightmare to pipe all these to preheat incoming water.
How will you decide which drain or drains to put the device on?
(The diagram shows the shower, but in my two-retiree household I don’t think it is the main hot water user - I don’t know which is.)
8 Dan // Jul 1, 2008 at 10:43 am
Hi Bill,
Thanks for the comment and thanks for stopping by.
From what I have learned this device goes only on the main vertical drain AFTER all of the connecting drain pipes from all of the other tubs, sinks, etc. have been connected to it. You actually cut the main vertical drain at the top and the bottom, and replaced the cut vertical drain pipe with the DWHR pipe.
As another article in this series will state, we are not installing it because our main drain in the basement was covered by a wall in the finished 2 piece bathroom in the basement which itself has the sink, mirror, etc. so way too much work for me to get to when I have other more pressing needs.
I hope that helps,
Dan
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