Not sure if this is the best forum for this.

I’m trying to pick a circulating pump to move hot water from my primary tank downstream to my buffer tank (unpowered electric water heater). This will allow my primary tank (GE hp water heater) to heat both tanks. I have prepared piping to mount the pump to draw from a T in the primary tank hot water supply pipe and discharge to a T in the cold inlet pipe of the buffer tank.

For the pumping circuit pressure drop….. I have (2) ¾” brass T’s, (3) ¾” brass 90 elbows, (1) ¾” Cu long sweep 90 elbow, 1ft ¾” Cu, 6 ft combined ¾”braided stainless hose, and then inlets and outlets of both water heaters. The hot outlets of both tanks have factory heat traps, but I’m not sure what pressure drop would be across these. For flow I only need to exchange about 50 gallons at a time, so I’m guessing anywhere from 2-8 gpm would be fine.

Can someone help me sort through my choices?
Which brands are preferred for an application like this?
Any brands I should avoid ?

Here’s some options I found…

B&G- http://www.grainger.com/Grainger/BELL-GOSSETT-Circulator-Pump-5JPA9?Pid=search

Grundfos- http://www.buyplumbing.net/UP1016BN5ATLC-Grundfos-Comfort-1-33-HP-Recirculator-Pump-with-NPT-Connection.html

Laing- http://www.buyplumbing.net/SM909BSW14-Laing-High-flow-Recirculation-Pump-3-4.html

Taco - http://www.grainger.com/Grainger/TACO-Circulator-Pump-4YVF7?Pid=search#

Watts -http://www.amazon.com/Watts-500800-Premier-Water-Recirculation/dp/B000E78XHG

Top of my head answer - as small as possible.

Grundfos up15-58 FC, 3 speeds manually selectable, its cast iron.

if this is Domestic hot water, be sure to use a bronze pump not cast iron. Many of the manufacturers now have very energy efficient pumps such as Grundfos Alpha that automatically adjust speed. Brand is not all that important until you get down the road to replacement time, many years away.

The Alpha - while a find pump - is inappropriate for this application.

See:


http://completewatersystems.com/wp-content/uploads/2011/04/LTBR-23.p

Jokin, I do a similar thing, but I let the pump on the de-superheater do the work. I have a line from the drain of the main tank connected in parallel with the in line to the de-superheater. If I open that valve the desuperheater pump on the geo unit will pull a small amount out of the main tank forcing the pre heat tank to move water in to the main tank. If I leave the valve shut at get the pre tank up to say 140F and the main tank is 100F and open the valve even of the geo is off the hot water will move out of the top of the pre tank in to the main tank and cold water will flow out of the main tank in to the bottom of the pre tank.

But when the geo is running it does mix them both and both tanks will heat up. I really need to put a check valve in line so when a shower is running the cold water doesn't move from the bottom of the pre tank in to the bottom of the main tank. But I am concerned the check valve might not open with the small amount of suction from the circ pump on the geo unit.

It would be neat to use a small pump like you suggest and wire it to a thermostat on the pre tank so when the pre tank hit 130F it turned the "mix" pump on until the pre tank hit 110F or something.

Maybe someone else has already figure a better way to take advantage of that extra de-superheat?