Building on this post....

Building on this post....
by ndroman21 (2019-08-23 10:54:08)

In reply to: The system does not waste water, it recirculates it. posted by voidoid

....hot water supply systems are usually built as a straight line run from the water heater to the nearest fixture to the next fixture.....so on and so forth, until they end at the furthest fixture from the water heater.

If you make the system a loop by installing a small (usually 1/4" or 3/8") line back from the furthest fixture to the water heater, you can keep a small amount of hot water constantly circulating through the line.

There are two methods for this. The gravity method works if you have a significant elevation change between the water heater and the last fixture (for exxample, WH is in basement, last fixture is on the 2nd floor). Because hot water is less dense than cold water, gravity will keep a constant flow of hot water rising in the line, and the colder water will travel back down through the re-circ loop.

If there isn't enough elevation change for gravity to do the work, a mechanical pump can be installed to do the same thing, with a thermostatic valve that activates the pump when the water at the last fixture cools.

As voidoid noted, this doesn't waste water, it wastes a small amount of energy heating water that may not be used at that time. But becasue the recirc line is ususally small, there is very little water being reheated.

It sounds like the pump

would be a lot less invasive/expensive to install than a line though, right?

Our master bath is on the second floor, farthest from the water heater (which is in the basement), so plenty of gravity drop. But seems like running a line from there back to the heater would be quite the ordeal.

Yes - the pump is basically the "DIY" version of the loop.

Building a home from scratch, you would do the loop. When we remodeled, the pump was like $300 installed versus running the new loop line under slab, through walls, etc.

You need the line with either method.

The valve doesn't dump water down the drain, it recirculates it through the recirc line.

Dumping it would waste water and energy, and is likely not allowed.

It's hard to say exacty how tough it would be to run the line. If you have a plumbing stack to follow, you might only need to cut a couple of holes in the walls in a couple of places to drill a new hole through the sill plates/heads. You can fish a 1/4" or 3/8" copper line through a stud cavity pretty easily.

Not true - the pump re-circulates through the cold supply.

We installed it at my house, works great, no loop required.

Hmmm, interesting. *

Yeah, this is what I'm seeing.

The original pump linked, the Watts 500800, says installation simply requires installing in the pump in the line and sensor by the furthest fixture.

As a fellow resident of CT

I wholeheartedly recommend it. During the dead of winter it is AMAZING to have immediate hot water.

It's all but a done deal. I had no idea something like this

even existed.