Our house has only one water heater for the entire place. It is a (pretty big) 75 gallon unit in the basement.
To avoid wasting water by having to run the water to get it hot, we have two circulation loops in the house. Being very long loops, they take quite a while to circulate the water and get it hot at the farthest location. Because of low pressure at the street, some of our inside water lines are quite large (1 1/2″ or 2″, I forget). This means the volume of water we are moving around with the recirculating pump is rather large.
If heat loss wasn’t an issue, I’d just leave the recirculating pump running 24/7. But alas, it is an issue. Even with our hot water lines insulated with the standard insulation, it actually burns up quite a bit of natural gas keeping the water hot all around the house.
The trick then becomes a balancing act between wasting natural gas, or wasting water. Both cost money.
The natural solution is to put a timer on the re-circulation pump, so that it only runs when you are likely to use the water. Some pumps come with such a time integrated in. A standard timer looks like this
But there are some downsides. You have to guess a schedule for timer like this. We usually shower at 7 am and / or 6 pm, so I’ll set the timer to run from 6 am to 7 am, and 5 pm to 6 pm.
If you guess wrong, or your schedule changes on any particular day, you are wasting gas and wasting water.
Leaving on vacation? Then I have to go down to our basement and unplug the timer. Coming back from vacation? No chance the shower water will be hot, because I have to plug in the timer first.
I found a better solution recently, a WeMo timer. I guess this qualifies as a smart plug.
