Full Recirculating Pump System - Which Pump

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winesalot

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I am getting ready to build and want a full recirculating pump system. When I look at supplyhouse.com or other sources I only see pumps/systems with the crossover valve to be used at your furthest sink. It will be a simple prospect to plumb a single main hot water supply line with tee's for each use and then return that line back to the water heater and, of course, insulate the entire length. My issue is it seems like over kill to put $400 pump on top of the water heater (or in that vicinity) and pump the return hot water in to a tee on the cold water supply to the water heater. If the pex is well insulated it seems to me that a trickle of water being pumped back to the water heater would keep the entire hot water system hot. Why are these pumps so big? Is there a smaller pump that will work?
 

Jadnashua

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REcirc is often required in places like hotels, motels, and larger office buildings as they will provide the health code's requirement for hot water in places like restrooms. As a result, with larger supply lines, to move enough water to do much, you need a larger pump.

In a residence, there's no reason to use a huge pump, and there are reasons to avoid them. On a hot water line, the Copper Institute calls for a maximum of 5fps velocity in hot water lines. With a 1/2" pipe, that's only 4gpm (8gpm on a 3/4" line).

I just replaced a failed under sink unit that lasted 15+ years with a new one. Couldn't get the required, proprietary part. The new system's pump draws all of 14W. A Hp is about 745W or 14/745=0.019 Hp...IOW, small. Seems to work fine.

You may still want valves in your system. Most systems shut off circulation when the water approaches 105-degrees or less (mine does it at 95 at the furthest location). That provides hot nearby that sink and almost instantaneous elsewhere AND limits the energy loss. The bigger the delta T, the more energy you'll lose in the supply and return line. A small pump also limits the wear on the pipes from erosion and keeps water flow noises essentially non-existent.

Many of the systems can be run with a dedicated return line instead of using the cold water line. I ended up with a Lang system. I saw prices from less than $300 to more than $800 for the same thing, so searching around can save some serious money.
 
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