Taco 5000 Series mixing Valve Problem?


Old 06-25-11, 04:02 AM
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Taco 5000 Series mixing Valve Problem?

We just had a new hot water tank installed and it seemed to be OK but we noticed last night that the hot water just wasn't lasting more than a very few minutes.

I think the problem is the Taco series 5000 mixing valve. Hot water is coming out of the tank to the valve I can feel it. But past the valve - leading to the rest of the house - it doesn't seem as hot. There is an inline thermometer right above the valve that shows 120 degrees but as soon as you turn on a faucet it starts to drop in temp to about 80.

The tank is fired from our oil boiler and that seems to be working fine - the boiler comes on eventually when the temperature drops. Again, the proper pipes in and out of the tank are hot.

Here is what I have checked: I pulled the cap off the mixer and tried adjusting it. Turning it all the way in reduced the temp on the thermometer to about 60 degrees. Turning it out all the way brought the temp back up to almost 120 (but it should be adjusted out all the way, right? First clue that it might be a bad valve?) I also noticed when adjusting the valve there were a few drops of water that leaked out of the valve adjuster. Second clue it might be the valve?)

So does it seem to be the valve? I'm thinking it just might be a coincidence that it went out when the tank was changed. The plumber is coming back out this morning but I'd like some reassurance. Thanks!

Last edited by calelettus; 06-25-11 at 04:30 AM.
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Old 06-25-11, 02:16 PM
Join Date: Mar 2006
Location: Wet side of Washington state.
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What temperature is the water heater set to maintain? With an indirect water heater (heated by boiler water) AND the tempering valve (mixing valve) you should maintain about 140 degrees F. in the water heater tank. If the plumber set the water heater thermostat to the more common 120-125 degree temperature that directly heated (electric, gas or oil) tanks are set for then the mixing valve hasn't got a chance of working properly.

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