The Tank › HW Drain pressure at 92?
- January 16, 2011 at 10:39 am #14958
After reading some of the posts I bought a pressure gauge and connected it to the drain valve on my HW.
I’m getting a reading of about 92 lbs. It stays the same if I open cold or hot water taps in the house. I have a backflow preventer in the main line from the water meter that is about 20 ft from the WH.
Is this an acceptable amount of pressure?January 16, 2011 at 11:07 am #14960
92 is high and, if constant, can damage and accelerate wear in many parts of your plumbing and appliances. Does the reading waiver at all when a hot or cold tap is opened? Have you tried a reading at another point in the system, such as an outdoor faucet? You mentioned your backflow preventer, do you have a pressure reducer or a thermal expansion tank?
ChuckJanuary 16, 2011 at 11:44 am #14961
I’m getting 80lbs on my utility sink faucet and an outside faucet.
I don’t have a pressure reducer or expansion tank.January 16, 2011 at 12:03 pm #14962
80 is about the upper limit. The 92 at the drain valve is interesting. Have you tried draining a gallon or two of water from the heater? If so, was the flow about what you see at the outdoor faucet? If not, perhaps the drain valve is reduced or clogged with sediment.
I would run a good amount of hot water from the utility sink or just after a hot shower; attach the pressure gauge to the utility sink and don’t run any other faucets in the house as you watch the gauge. As the water heater recovers back to it’s set temperature and shuts off, what is the pressure reading? I would expect the reading to climb to some peak until the water heater shuts off.
In most systems that have a backflow preventer, some means of dealing with this thermal expansion is needed. As the water heater reheats it’s contents, the water, which is nearly incompressible, expands when heated. This boosts the pressure in the closed system until a faucet is opened somewhere in the house and the pressure drops back to the supply pressure.
A Thermal Expansion Tank is an easy addition to deal with “thermal creep” The tank and a few fittings to attach it to the cold water supply near the water heater should cost less than 100 dollars.
ChuckJanuary 16, 2011 at 12:16 pm #14963
If you supply pressure is constantly 80 psi, I would consider adding a Pressure Reducing Valve to the supply line to drop the pressure to between 40 and 60 pounds. This will not only reduce wear in your system, it will reduce consumption (and your water bill). This thread:
has a good discussion on pressure spikes.
ChuckJanuary 16, 2011 at 8:57 pm #14965
I have a leak in the WH which is why I’m paying attention to the plumbing. I’ve drained the WH already and there is no visible sediment in the tank or valve.
Is the pressure on the drain valve higher (92) than the other taps (80) because of the pressure of 40 gallons of standing water in the WH, or because of thermal expansion from the gas heating the water?January 17, 2011 at 12:58 am #14968Larry WeingartenParticipant
Hello: You might double check the reading at the heater at different times. It should be essentially the same as the rest of the house if it’s level. Otherwise the difference in pressure would suggest the heater is over twenty feet lower than the house…. and that’s somewhere between unlikely and silly 😛
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