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Mike R.
Mike R., Plumber
Category: Plumbing
Satisfied Customers: 2688
Experience:  20 years of plumbing experience, including high end homes and service work.
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I recently replaced an old (early 80's vintage) Moen valve

Customer Question

I recently replaced an old (early 80's vintage) Moen valve trim with a new Voss Moentrol valve trim kit. I used the Moen 145058 Valve Adapter kit to do so and all went fine. Nothing else was changed out--no valve or plumbing changes of any kind. No change in water heater or anything.
But NOW, like "clockwork", the shower changes from HOT to COLD every 5 minutes. After a minute or two at COLD, it returns to HOT. But then 5 minutes later same happens.
Have you ever heard of this? Any idea how to correct? We have two other showers in the house and none of them exhibit same behavior. And this one never did before the valve trim change either.
Thanks.
Submitted: 1 year ago.
Category: Plumbing
Expert:  Mike R. replied 1 year ago.

Hi my name is ***** ***** I have been in the plumbing field for 20 years. I will be glad to help you today. If you turn the water off on the water heater, do you still get water out of that valve when you turn it on?

Customer: replied 1 year ago.
I have an instant/on demand water heater (which I have had for years), so not sure if the question applies.
Expert:  Mike R. replied 1 year ago.

Yes, the result will be the same. There should be no water with the water heater turned off. If you have a circulation system then turn the pump off too.

Customer: replied 1 year ago.
Just so I understand correctly (because it sounds very strange to me)...are you saying that if I turn off my instant water heater, I will not have any water anywhere in my house? I would think I would still have cold water coming out. ?? I do not have access to it right now anyway so will not be able to do anything with it until tomorrow.
Expert:  Mike R. replied 1 year ago.

This is just to test the valve. The valve is pressure balanced so if you turn the hot water off then you should have no water in that shower or any shower since they are all pressure balanced valves. Anything that is not pressure balanced will have cold water only. This is only a test and once you know the result then you can turn the hot water back on.

Customer: replied 1 year ago.
Ah, I see. Thanks. So, is it okay if I do that tomorrow when it is light? (The water heater is in an area that has no lights, and of course it is dark right now.) I also have not looked at it since first installed 8 years ago so not sure I know how...but assume it will be pretty obvious. Will advise once that is done.
Expert:  Mike R. replied 1 year ago.

Sure thing. That is totally fine. Almost certainly the issue is the pressure balance cartridge. The test may or may not confirm the issue. If the water does turn on at all with the water heater off then it certainly is the pressure balance cartridge. It very well could be fixed without replacing it. You would remove it and take the piston part out of the middle and grease it with some plumber grease or silicone grease. Never use any petroleum products like Vasoline or oil. They will eat the rubber gaskets and only cause issues. click here If you changed the trim yourself you likely saw the big screw to the left of the mixing cartridge with a big flat head screw. That would be the cartridge. It almost certainly is the problem so if you would like you could skip the test and just lubricate the cartridge.

Customer: replied 1 year ago.
Ok. Would there be any direct correlation between just changing the valve trim and this cartridge now suddenly (after the change) needing lubrication?
Expert:  Mike R. replied 1 year ago.

Had you turned the water off when doing the change? Was the valve regularly used before the change?

Customer: replied 1 year ago.
we turned off water during change. This shower is guest shower so was NOT used regularly.
Expert:  Mike R. replied 1 year ago.

The turning off the water and non usage would be the cause along with the age.

Customer: replied 1 year ago.
you think issue with pressure balance cartridge will cause the behavior as described...that it goes back to hot again after a minute or two...then cold again after 5 minutes? in other words, changes back and forth?One other clarification for the test I will conduct tomorrow...do you mean that I need to turn the WATER off to the water heater, versus turning off the water heater itself? (sorry for the dumb questions)
Expert:  Mike R. replied 1 year ago.

The only dumb questions are the ones that do not get asked. Yes. Just turn the water off. With a pressure balance valve if the water pressure changes on one (hot or cold) the other is reduced the same amount to reduce the chance of scalding and keep the temperature even. The pressure changes a little and the cartridge sticks then comes loose. Really, if the water heater is any kind of inconvenient I would suggest just removing the cartridge and taking it apart and lubricating it. It almost certainly is that. You could always get a new one. Moen would send one for free but it is repairable also. Turn the water off to the house and remove the trim and plate to expose the big flat head screw and remove the stem (to the left of the mixing valve that the handle is connected to) then take the piston part out and rinse it off then put a little plumber grease on it and be sure that it can move freely then replace it.

Customer: replied 1 year ago.
Okay. I will try that.
Expert:  Mike R. replied 1 year ago.

Good luck, we're all counting on you!

Customer: replied 1 year ago.
Thanks. I need all of the luck I can get!
Expert:  Mike R. replied 1 year ago.

You are very welcome. Let me know if something comes up. I will not be online a lot tomorrow morning but should be in the afternoon. They sell the plumber grease at Lowes and Home Depot and pretty much every hardware store. click here

Customer: replied 1 year ago.
My apologies for not getting back. I have bought the plumbers grease but have had issue getting the valve trim off as I don't have proper tools and have not yet had a chance to get them due to friend moving in this weekend. Probably won't be able to do it now until Wednesday. So I really have no idea yet if this will correct the problem.
Expert:  Mike R. replied 1 year ago.

That's totally fine. Just be sure to get standard allen wrenches and not metric if you need allen wrenches. The kit should have come with one. It may be with the manual if the installer was mindful enough to leave the manual.

Expert:  Mike R. replied 1 year ago.

I haven't heard from you. Was the information I provided helpful?

Expert:  Mike R. replied 1 year ago.

So, are there any more issues that i may assist with?

Expert:  Mike R. replied 12 months ago.

Were you able to fix the issue with the information provided?

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