Water heater has "released" water from T&P reliefe valve a few times

Old 12-29-16, 06:01 PM
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Water heater has "released" water from T&P reliefe valve a few times

So our water heater is a separate propane water heater. Water is not pre heated from our oil burner. Only the burner has an expansion tank, no such tank on my heater tank. heater tank is filled with direct line water inlet.

It is about 8 years old, regularly drained with no sediment noticed.
Went away for 5 days and dropped house temp to 60 ( have wifi water leak detector next to tank)

About 5 hours before we got home after 5 days I set the house to 68 degrees( note the water heater is nto preheated by the boiler)
20 min before we get home we get a water leak detection. about 8 ounces has leaked out of the down pipe

Odd i thought. Cleaned it up water was inside the pipe thus the T&P valve released .. but why now?

3 days later it releases again. I was notified by the water leak detector ( I have always had a leak detector by the heater for the past 4 years, never went off) no change in house temp this time ( heater is in basement no direct heating)

Any insight? as to why? I Understand why the T&P valve is there but not sure why after all those years? Only other thing I can state is that the fitting on top of the heater had a lot of buildup, but now no loner does. Need to check if the insulation is wet

Any ideas?
Old 12-30-16, 02:51 AM
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Things age, so some points to ponder. The T&P valve is old and needs replacing. You have no expansion tank on the incoming water line giving expanding water a place to go, thereby actuating the T&P valve. Your incoming water pressure is way above 65 psi and is causing the T&P to actuate. The water temperature is set too high and is causing the T&P to actuate. Just some things to consider.
Old 12-30-16, 04:52 AM
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I would start by replacing the T&P. They do tend to leak with age. If the new one discharges also then I would start looking into other causes and remedies.
Old 12-30-16, 10:08 AM
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I would start by checking incoming city water pressure. If you find you have pressure above 65 psi, like Chandler mentioned, you need to install a pressure reducing valve and an expansion tank. If incoming pressure is below 65 psi you probably won't need the PRV and just need the expansion tank. If you still have the problem, replace the T&P relief valve with a new Watts valve.
Old 12-30-16, 11:09 AM
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Expansion tank use must vary by location. I have never seen one used in my area. Not saying they are not useful just commenting.
Old 12-30-16, 12:46 PM
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soem good points. I
ll begin with replacing the valve first ( easy and cheap)

back story is we do have pressure reducing valve ( always have for past 25 odd years)
PSI is about 80 and has been for past # of years
The PRV was replaced this past spring? due to age.
I'll update after I replace the TPR valve

thanks for the ideas..... Id liek to stay away from the expansion tank. as for reducing the water pressure i'm loathe too as we liek the pressure that high and like I said have never had the leaking
Old 12-31-16, 09:07 AM
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I say that the first order of business is installing an expansion tank, best location is above the water heater on the cold inlet without the shutoff in between.

The expansion tank for the boiler is on a separate water circuit and will not protect the water heater and domestic plumbing.

If there is no pressure reducer or check valve on the incoming cold water from the city water main then you can get away with no water heater expansion tank becsause the water will expand back to the water main.

Fo a well pump system the pressure tank will act as an expansion tank for the water heater so long as there are no closed valves or check valves in between.

Measure water pressure several times using this method: Wait until the water heater burner is off. Draw out two cups of cold water. Turn off all faucets. Measure the water pressure (anywhere in the domestic plumbing system). Of about half a dozen measurements take the smallest value. Preset the water heater expansion tank to this value before installing or after cold water has been running moderately fast for a minute and is still running.

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