Budget Hot Water Recirculation Via Cold Water

[Baumgrenze]

I am a new duplex/cottage resident in a CCRC. I'd like install (and perhaps to promote) a working but not super expensive under the sink hot water recirculation pump, manual start, for a bathroom where at best I must run the hot water over 1 minute (a good sink full) before the water is warm enough to use (and that is in the summertime when the attic is warm to hot.) I can no longer check but I suspect that the lines have no insulation. The water heater is a tank, electric, so at least the water could be recycled. Recirculation would also save on electric costs, wouldn't it?
How do I justify this in cost recovery terms? How long is the approximate payback period?
The same I true for the simple urethane insulation I installed in my furnace room when I was a homeowner. In the long run it must save money, no?
Thanks,
baumgrenze

 

[Phog]

How do I justify this in cost recovery terms? How long is the approximate payback period?

Your premise is wrong. A recirculation system will increase the electricity usage, not decrease. It takes extra electricity to operate the recirculation pump. Recirculation also will increase your standby losses, making the water heater turn on more often (unless you are on a triggered system, which means you press a button about 60s before you start using hot water to trigger the recirculation). The only savings will be on your water bill, since you will no longer be wasting water while you run the faucet waiting for hot water. Sorry for the bad news.

 

[Sponsor]

 

[Jadnashua]

Assuming you pay for your water and sewerage (that is often based on your water usage), and you can insulate your water lines, and you use a timer so that the recirculation system only runs when you tend to use hot water, studies have shown it saves money. Even if you have a well and a septic system, you still pay to pump the water out of the well. But, yes, the unit does cost, so it may never pay back the cost to install. The convenience, OTOH, of having hot water without having to wait is a really nice.

Keep in mind that say it takes a minute or more to get hot water...depending on the valve, that might be a couple of gallons of hot water that you've paid to heat, depleting the volume of your WH by that amount since cold is filling in to replace it, and dumped down the drain as essentially waste. Depending on where you live, water is a precious commodity, and a recirculation system saves water.

The pump I have on my system only draws 9W when running, and it only runs maybe 6-minutes/hour...less than a night-light. If your water lines are well insulated, your losses are not huge. What some systems use (not a good idea in my view) is a large pump to get hot water there quicker. That does several things:
- pumps water faster than the Copper Institute recommends that can cause extra noises and literally erode the pipe from the inside
- uses a lot more power (ChiliPepper is one model that chooses to do that).

Most of the systems use a small pump and the function runs as needed, not necessarily continuously. The costly part is that the pump must be either stainless steel or bronze...a circulator pump as used for heating your home won't work as the impeller and maybe housing will just rust away in the potable water that contains dissolved oxygen.

 

[Baumgrenze]

I see now I should have been more direct in my first post.

Which pumps have users and plumbers found that work when the user wants to run water back from the use point to the water heater via the cold water line using an 'on demand' switch that recirculates via the cold water line and a check-valve under the sink at the furthest point from the water heater.

Has Grundfos accepted the error of their conclusion that their 'Autosense' approach is so superior that their Comfort System pumps cannot run with Autosense disabled so that they can be used with a timer. I appreciate that their pump mechanisms have a pretty good track record.

Are there other pumps worth considering? Is one check-valve better than the others?

Thanks
baumgrenze

 

[Breplum]

All the bridge systems using the cold water pipe are pretty crappy, delivering warm water at the cold spout most often.
All the brands are ok.
(ACT) D'Mand make fine systems, Grundfos is fine. Taco is fine. The user initiated switch is definitely the best way to go.
Dedicated return lines are the absolute best way to go, of course.

 

[Jadnashua]

It depends somewhat on your expectations. On the system I have, it shuts the pump off when the water at the cross-0ver gets to about 95-degrees F. There are some that are adjustable. Some close the cross-over at like 105-degrees. What I find with mine (and it uses the cold water for return) is that if you flush the toilet, that purges almost all of the warm water in the cold water line, but even if you don't, the warm water there is not much warmer than the middle of summer.