View Full Version : Plumbers/plumbing hobbyists

88 PS190
07-16-2008, 01:14 AM
Looking for an opinion here... not necessarily cold hard fact but a place to start looking.

Problem: New dental office, hot water getting into cold water pipes.

Elements in the system that I am atleast someone convinced are to blame.

Bell & Gossett Recirculator pump (pushes hot water through the lines, therefore each hot water faucet has a return that takes it back and should stick it in the tank.

There is also a tank, approx 1 gallon that has a shraeder valve. This tank I believe is utilized to deal with surges in pressure/impulse when water is turned off and expansion of water in the tank.

Now the way the plumbers set it up seems to be that the hot water return line comes into the cold water line into the tank, I do not see any sort of check valve.

Has anyone ever installed a recirculator pump? How is the hot water return normally plumbed into the system? Are their check valves that are heat sensitive to prevent temp back flow?

There is one other possibility that I don't even want to believe. Architect specified a valve much like a shower rotary for the wash basin in the dark room, (ADA wash basin) plumber could not source the equivalent basin/valve as spec'd and supplied one with separate hot/cold valves. But potentially plumbed in a mixing valve previously... time will tell.

Either way GC has been notified, as have plumbers according to GC. And it is a priority on our punch list, but if there was anyone who could confirm I could fix our problem and not have to run cold water for an hour to flush the hot out of the system.

07-16-2008, 09:10 AM
I am a hobbyist. I have fully plumbed several of my homes but have yet to put in a recirc loop. I know the general idea. It definately sounds like you need a one way valve where the hot comes into the cold. I would bet that is your problem source. I know there are usually one way valves installed so you don't get back flow on recirc systems. If there are none then that is the cause. My 2 cents.

07-16-2008, 10:17 AM
There should be a check valve just before the hot water return line enters the water heater. It can be a standard hinged/flapper type if it is on the horizontal run but, if it is installed on the vertical run, a spring check valve is recommended as with a hinged/flapper type installed vertically (aiming down) the flapper will hang open and will not ensure a positive check. Any tempering valve or mixing valve should not be a problem as they are designed to check themselves or even 2 seperate (Hot and Cold) valves should not cause the problem as the water pressure should balance and check each other. Rick

07-16-2008, 10:22 AM
I have to add for clarity that the check valve should be installed on the return line - after the pump itself - before the connection into the cold supply piping. The 1 gallon tank is an expansion tank and should be installed on the cold water side ahead of the cold water heater inlet and has no bearing in the issue at hand.

07-16-2008, 11:05 AM
Attached to my post is our standard Gas water heater detail with recirc pump.

You should be able to follow the diagram and figure out what might be missing