Plumbing Questions? Ask a Plumbing Expert.
Hi my name is ***** ***** I have been in the plumbing field for 20 years. I will be glad to help you today. I have a few questions to start with. Is this a pressure balanced shower or thermostatic shower? Is it a new installation? What type of water heater do you have? Does the shower have separate shut off valves and if it does are they on the piping or are the shut offs integral?
If you remove the shower head does it do the same thing? Does the water pressure seem to be low? Are you sure that it is pressure balanced and not thermostatic? Do you know what model American Standard valve it is? Some valves have built in shut offs that you may not even know are there. You would have to remove the face plate if you are unsure that it has them. On the ports where the hot and cold hook up to the valve body you may find very small flat head screws. These would be shut offs. The issue sounds like shut offs that are partially off and the restriction would cause exactly what you have described. Sometimes with time the screws will slowly turn on their own from the vibration of the water.
If there are certainly not shut offs then another issue that would cause this would be a pebble or some sort of debris getting caught up in the inlet port. The debris could be a piece of glue if you CPVC water piping. Not a lot of installers know clearly how to install that type of piping. If you remove the cartridge then turn the water on and then off to flush it then install the cartridge again and also check for the screws and if there are screws as described be sure they are all the way open. It would be quite handy if there are shut offs too, for flushing the valve as described.
You are very welcome. I will also explain why I think that is the issue. If you were to turn one of your shut offs partially off under one of your sinks it will very likely hammer from the restriction. That would be why it hammers like it does. If you have city metered water and you have had water pressure issues in the past and the problem was solved by turning up the pressure we will want to discuss that also. Anyway, so the water being restricted causes the hammering and when the hot water is restricted then the flow is slower. The restriction must be on the hot side and when the hot water is slowed then the flow is not strong enough to keep the water heater heating the water so when the water heater stops heating for a few seconds you will get bursts of colder water. So, carry on with the plan and let me know how it goes. If the water pressure situation I am guessing about was an issue we likely should have a phone conversation about that. There would be a fair amount to discuss and would be much easier on the phone. I will be away for most of the day tomorrow on a job but I will check in when I can and reply as soon as I can.
Btw the reference to the sink shut off is only an example and is not meant to be anything that is causing issue for you.
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I would be happy to continue to help if there is any more I can offer?