Hot Water Heater Mixing Valve Question


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Old 12-10-13, 04:56 PM
L
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Hot Water Heater Mixing Valve Question

Hello. I have a question regarding thermostatic mixing valves. For background, the hot water was lasting only 5-10 minutes before going cold and staying cold. Previously, I noticed the (shower) water would go cold for a couple of minutes and then gradually come back hot. This is in a new-construction condo built in 2005. I called a professional and he diagnosed a failed mixing valve which he replaced and everything appears to work as expected now. So my question is are these valves a planned-obsolescence-type part or are they serviceable somehow where you can replace the thermostat or whatever part of the valve that wears out? Also is there anything I can do to preserve or prolong the life of the new mixing valve? Thanks very much.

LH
 
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Old 12-10-13, 05:06 PM
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So my question is are these valves a planned-obsolescence-type part or are they serviceable somehow where you can replace the thermostat or whatever part of the valve that wears out?
Isn't everything these days? It's a 'throw away' society we live in.

Some of the valves DO have replaceable guts. Usually the cost of the guts is equal to that of a new valve, but would enable one to simply rebuild the valve rather than replace, so perhaps easier, and within the realm of DIY.

is there anything I can do to preserve or prolong the life of the new mixing valve?
I don't think so... 8 years is pretty good run I think.

Moving your post from 'HEATING SYSTEMS' to 'WATER HEATERS'.
 
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Old 12-11-13, 04:36 AM
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From my experience in the industry, I have found a great number of DHW recirculation lines installed incorrectly where it comes to the anti-scald valve.
The recirc pumps need, at minimum, an aquastat to turn them off once the return water temp is above 90F. A timer is another recommended addition.
No need to be circulating DHW thru the building while your asleep or away at work.

The anti-scald valve needs to be able to draw a portion of the returned back into itself to cool temper the hot water it sends to the fixtures.
I have seen very expense 1 1/2" mix valves ruined in 6 months due to a large recirc pump and no control other than an on-off switch.

I have seen anti-scald valves last 10 plus years.
 
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Old 12-11-13, 07:10 AM
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Thanks for the replies and putting my post in the appropriate forum.

In looking at the instructions that came with the valve (caleffi series 521) this appears to be a throw-away part. It does describe removing limescale by immersion in de-scaling fluid but that is beyond my current DIY skillset. So unless that changes I'll be calling in the pros again.

I'm not sure if my system has a recirc pump but if I had to guess, unless required by code the economy minded builder left that out as well as an expansion tank. Also if I understand it's purpose correctly, since the distant faucets take a while to get hot water I'd guess I don't have a recirc pump.
 
 

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