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Shower goes from scalding hot to ice cold with a slight turn of the knob.

joecap5's picture

I can't seem to get my shower temperature under control. The water often is extremely hot or ice cold. I can get it to stay at a lukewarm temperature for a long enough time to take my shower.

If it is too hot  I turn the knob just slightly and the temperature will swing wildly and become really cold. The reverse happens as well.

I tried replacing the ball valve, seats and springs but there wasn't an improvement. I didn't see anyway to remove the socket so I could put a completely new or different type of valve in.

I have a boiler system without an external water take. The hot water is generated right inside the boiler. I know this is why the temperature can be so hot and if left at a high enough flow rate the hot water will run out. But I seem to be haveing an additional problem with the temperature swinging back anf forth with extremely small twists of the knob.

Could anyone provide any ideas about what the problem could be?

FYI, I recently moved in to my house so I only have a couple months experience with the hot water.



It's hard to say if you have (post #209301, reply #1 of 6)

It's hard to say if you have a pressure balancing valve.  If so, behind the main valve mechanism is a sort of piston that slides back and forth to keep the hot/cold pressure equalized.  If the piston is stuck you can have this symptom.

Otherwise, installing a "tempering valve" where the hot water exits the boiler (or in the wall behind the shower, eg) may help.  This is a valve that mixes cold with the hot, based on a built-in thermostat, to produce not-so-hot water at a steady temp.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

That's interesting. I'll need (post #209301, reply #2 of 6)

That's interesting. I'll need to take the plate off again and look at what I have behind the faucet.

If I remember correctly there is a big unit with pipes running in and out. I didn't see a way to get into it to before. It looked like it's just brazed in there.


Joe (post #209301, reply #3 of 6)

Can you post a link or list the manufacturer and model of the valve?

How old is this?

Perhaps a picture with the parts intact and then one of the guts in the wall?

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I would install a (post #209301, reply #4 of 6)

I would install a thermostatic mixing valve if there is no problem with the faucet.  Your incoming water temperature may be dangerously high, but I'm guessing on that.  You can adjust the mixing valve so that the temperature of the hot water remains constant, until the hot water temp falls below the set point.  If you set it right you can just take a shower with the faucet set to HOT and it will be right where you want it to be.

It's a delta ball and socket (post #209301, reply #5 of 6)

It's a delta ball and socket valve probably original from 1977. I attached a picture. Not much room to do anything. No access from the back.  I think you guys are right about the thermostatic mixing valve. Is there a specific type or are they ball just pretty much the same for home use? Any brands that are recommened or recommened for avoid?

Thanks a lot!

20140208_123612.jpg1.79 MB

Yeah, that looks like the (post #209301, reply #6 of 6)

Yeah, that looks like the Deltas that were original in our house in 1976.  They were relatively inexpensive (but fairily durable) valves that would not have any sort of pressure/temperature balancing.

Since you complain that you don't have much hot water reserve, probably the best thing to do is to install a tempering valve (or "thermostatic mixing valve") on the water heater.  This limits the temperature reaching fixtures, regulates the temperature, and effectively increases water heater capacity.  I saw a unit at Home Depot yesterday that was priced at $99, designed for (experienced/lucky) DIY installation, and others are listed online starting around $85.  I would guess a plumber would install one in an uncomplicated situation for maybe $250 in most parts of the country.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville