Shower has intermittent good and low water pressure

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Old 12-13-12, 02:04 AM
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Shower has intermittent good and low water pressure

I am a new plumber and the shower/bath at my new house is stumping me, before I go out and replace the guts its a moen single handle faucet wondering what could be the cause. The water pressure starts off good then slowly decreases. If I push the lever diverter and pull back up shower pressure is good again, then cycle starts over from good pressure to almost nothing. House has copper plumbing and is single story with a recirc pump.
 
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Old 12-13-12, 07:56 AM
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Run the shower & hold the diverter up by hand. Does the pressure still decrease?
 
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Old 12-13-12, 08:15 AM
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Do you push pull to activate the water or turn?

Is this a new problem or long going?
 
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Old 12-13-12, 04:29 PM
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Is it a pressure problem or a flow problem? There IS a difference.
 
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Old 12-18-12, 07:35 AM
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held diverter up by hand did not correct problem, also seems to be happening when recirc pump is on, start up shower flow is good then gradually decreases to a trickle, resetting the diverter lever will bring back normal flow, then minute later gradual loss of flow.
 
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Old 12-18-12, 08:16 AM
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Is the pressure dropping when the circulator pump for the baseboard heating runs? Are you saying that you don't have a separate hot water tank, that it's just a coil in the boiler?

If that's the case, I don't think that you need a new divirter.
 
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Old 12-18-12, 08:37 PM
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single level ranch style house with a half inch recirculation line running from the water heater drain valve, with a recirculation pump on the line. Problem also only happens sometimes I cannot consistently re-create the problem. Even with recirc pump running.
 
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Old 12-18-12, 08:55 PM
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I will go out on a limb here.... I would say its the check valve that should be in line is sticking at times... This would be on the lower pipe from the water heater on the recirc line.

Probably a swing check. When that sticks it will cause an influx of cold water and/or cause the balance spool to adjust, hence reducing pressure.

You did not say if the water gets hot or colder with reduced pressure....
 
 

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