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Old 12-10-2019, 12:43 AM   #1
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New Shower Trick

Hi All,

My shower has learned a new trick and it's no fun

I have an '82 GB and the water temperature that comes out of the shower head pulsates back and forth between scalding hot and cold water.

I have three sinks (two heads and the galley) and this problem does not exist anywhere but the shower. I have a Jabsco Par-Max Plus water pump, but it seems to be above reproach given that this only happens in the shower.

Where do I start?

THANKS!
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Old 12-10-2019, 12:54 AM   #2
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Greetings,
Mr. Rl. "Where do I start?" Stop taking showers.


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Old 12-10-2019, 01:02 AM   #3
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Nice

I don't mind being dirty, but being single is another matter...
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Old 12-10-2019, 01:28 AM   #4
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Maybe a washer is loose and blocking the flow to one side??? Not an expert on plumbing for sure but I would take the faucet apart and look for something loose inside.
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Old 12-10-2019, 01:45 AM   #5
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Thank you

Thanks Comodave. That sounds like a reasonable possibility and I'll give it a shot.

Lucky
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Old 12-10-2019, 01:49 AM   #6
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Does the pulsating follow the on-and-off of the water pump. In other words, does it become scalding when the bump runs and cold when the accumulator is driving it between cycles?

I'm wondering about hot water expansion in the system or a bad accumulator or air trapped in the tank resulting in a higher hot water pressure than cold water pressure at certain times in the cycle? Does it go away or get better if a sink is left running hot water slowly?

Also, what about a leak letting air in near the shower and air daming the showers mixer or anti scale valve and then flushing out to accumulate again?

Or...as others have said a bad shower faucet or one with debris flapping around? Simpler failure mode, maybe.

-Greg
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Old 12-10-2019, 02:07 AM   #7
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Hi Greg,

Thanks. The pulsating is consistent from the time the faucets are open -- it does not follow the cycling of the water pump. Thanks for pointing out the other possibilities, I'll put them on the list.

Lucky
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Old 12-10-2019, 02:26 AM   #8
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Hey Lucky,

Does pressure change? For example, go down during the hot pulses? Or cold pulses? Or even go up?

Do the pulses have a consistent rhythm? Or random? What is the interval like?

Thanks,
-Greg
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Old 12-10-2019, 02:28 AM   #9
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Greetings,
Mr. Rl. "Where do I start?" Stop taking showers.


Ironically, that sounds like something Groucho Marx would say...
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Old 12-10-2019, 06:20 AM   #10
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There should be a working check valve at the HW heater to prevent warm expanded water from going back towards the pressure pump. See if its working.
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Old 12-10-2019, 07:11 AM   #11
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If it's only at the shower control, I would suspect the control itself, the plumbing just before it, or between the shower head / hand held sprayer and the control.

My inclination would be to work backwards. Start by removing the shower head / sprayer and see if the situation continues without it attached.

Ted
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Old 12-10-2019, 07:29 AM   #12
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Greetings,
Mr. Rl. Re: Post #3. EXCELLENT answer! Thanks. You'll fit right in here. I've nothing to add to the suggestions already posted.


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Old 12-10-2019, 08:12 AM   #13
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Maybe a washer is loose and blocking the flow to one side??? Not an expert on plumbing for sure but I would take the faucet apart and look for something loose inside.
That'd be my starting point, also. If there's something stuck in the mixing valve you might get symptoms like that. Find out what kind of mixer is installed and see if you can find the manual for it online. That would give you a head start on figuring out how to properly disassemble and service it.
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Old 12-10-2019, 09:38 AM   #14
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It sounds like the mixer valve on the shower might be sucking a little bit of air. If this doesn't occur with any other faucet, then you have to discount the tank, fittings and pump all the way to the only variable where behavior is different. (theoretically).
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Old 12-10-2019, 10:45 AM   #15
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It sounds like the mixer valve on the shower might be sucking a little bit of air. If this doesn't occur with any other faucet, then you have to discount the tank, fittings and pump all the way to the only variable where behavior is different. (theoretically).
I would agree. Sounds like air is entering your system. Just the hot side or cold or both hot and cold? Any leaks in the system?

Try disconnecting the shower hose at the mixer. Still have the issue at the mixer valve?

No? The issue is your shower head and/or shower hose to head.


Yes, you have an issue between the mixer and the hot water heater. Check your water lines from the mixer to the hot water heater. Check cold back to the first "T"

Good luck.
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Old 12-10-2019, 10:57 AM   #16
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Many systems have a mixing device such that the hot water is mixed with cold to make sure you don’t get scalded. Check that out?
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Old 12-10-2019, 11:22 AM   #17
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Post #10 would be the first thing to check.

An accumulator would dampen pulses.

If the shower valve is a domestic unit like the first picture, it may have a pressure balance valve built into it.

A pressure-balance valve is basically a standard single-handle mixing valve with one important addition: a pressure-sensitive piston, spool or diaphragm. When the hot water pressure increases relative to the cold pressure, it moves in one direction to limit hot water flow while at the same time increasing the flow of cold water. When the cold water pressure increases, it moves in the opposite direction to limit the flow of cold water and increase the flow of hot water. The ultimate result, in either case, is that the water temperature stays the same.

If there is debris in the pressure balance valve or you don't have a check valve as described above or the valve is bad, the diaphgram could be oscillating back and forth causing the pulsation. Replacing the cartridge may fix the issue.

Pressure balancing valves does not work as well on boat water systems with pulsating pumps, inconsistent pressure and slow temperature rise marine water heaters.

Install a true thermostat controlled shower valve like the Grohe Grotherm - second picture. That's what I have in Sandpiper and my wife can wash dishes while I shower with no temperature swings.
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Old 12-10-2019, 12:14 PM   #18
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If the pressure in the accumulator is not correct it will cause this problem. I have had this problem in the past, corrected the pressure, solved problem. Research what the pressure should be, check it with a tire gauge. Easy to do.
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Old 12-10-2019, 04:53 PM   #19
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Thanks

Hi Everyone,

THANK YOU for all your suggestions. Greg, the pressure does not change and the pulses do have a consistent rhythm. I would guess the pulses to be two to three seconds in duration.

Thanks again everyone and Happy Holidays.

Lucky
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Old 12-16-2019, 03:41 PM   #20
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We had exact same problem turned out to be incorrect pressure at our accumulator tank for what it's worth
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