Solving a potential Cross-Flow issue.

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Old 04-11-13, 10:15 AM
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Solving a potential Cross-Flow issue.

I recently removed my Recirc Pump ( Grundfos) on my Hot Water recirc system so that I could install service valves. I had difficulty sweating on the new valve, because I had a pretty good trickle of water coming from the recirc line in the house. The hot water input line had been shut off and the tank drained. I opened the faucet in the master bathtub full hot to help drain the pipes.

After 2 hours, I still had water trickling from the pipe ( about 1-2 GPH) , so I opted for SharkBite valves just to get the job done. In thinking about this, I believe I have some crossflow happening, and would like some help in a method for tracking this down.

The house is 4150 sq ft single level, with copper pipes buried in the slab. 5 bathroom showers, all with Moen single handle valves. Two of them are the Moentrol valves with balancing spools. The other three appear to be the more basic valve. I also have 4 sinks with single handle faucets ( two are Moen, One Price-Phister, the other unknown( installed behind the mirror of the bathroom sink!) . I'm focusing on the single handle installs, think this is the most likely place for crossflow to happen. There is no "Y" connector on the washing machine.

I'm thinking that I will remove the pump again ( easier now!) and after allowing the pipes to drain, begin shutting off the cold water supply at each of the single handle installations to see if the flow decreases/stops. Assume that any change means crossflow in that fixture, and a cartridge replacement might be the fix.

Anybody have other ideas? Would a sticking Moentrol Balancing Valve cause this issue?
 
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Old 04-11-13, 09:12 PM
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Welcome to the forums.

You don't realize how much water is left in the pipes until you want to do a repair.
I know I've seen water trickle out of a system for a long time. It depends on the amount of horizontal plumbing in the system. Normally I would open several faucets to let the system drain out.

Instead of turning off each faucet....... try turning the main off first and see if the flow reduces.
This way you'll know if it's just the pipes holding water or if you really do have a problem.
 
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