Expansion Tank
Top Answer
09-01-21, 03:58 PM
Preset the expansion tank to approximately the static pressure, 70 PSI. Ever few minutes during the presetting process (using an air pump) open a faucet upstairs so the expansion tank bottoms out at that approx. 70 PSI.
Seventy PSI in from the water main is a little on the high side for home pressure. For this I suggest a 3 or 4 gallon expansion tank.
I estimate that the worst case expansion is one gallon to heat all 50 gallons water up from an incoming 50 degrees F to 120 degrees. When that increase squeezes into the 2 gallon expansion tank the air cushion will have half of the space it occupied before, which means its pressure (and the pressure everywhere else in the system) will double making 140 PSI.
If you preset the expansion tank lower, say, to 50 PSI, the system pressure will still go to 70 PSI when all the faucets are turned off. With the lower preset pressure, water will go into the expansion tank even before the water heater raises its temperature. This leaves less space in the expansion tank for when the water starts expanding from being heated.
Seventy PSI in from the water main is a little on the high side for home pressure. For this I suggest a 3 or 4 gallon expansion tank.
I estimate that the worst case expansion is one gallon to heat all 50 gallons water up from an incoming 50 degrees F to 120 degrees. When that increase squeezes into the 2 gallon expansion tank the air cushion will have half of the space it occupied before, which means its pressure (and the pressure everywhere else in the system) will double making 140 PSI.
If you preset the expansion tank lower, say, to 50 PSI, the system pressure will still go to 70 PSI when all the faucets are turned off. With the lower preset pressure, water will go into the expansion tank even before the water heater raises its temperature. This leaves less space in the expansion tank for when the water starts expanding from being heated.
#2
08-29-21, 12:43 PM
Member
I found this when I searched. You need a thermal expansion solution that is adequately sized for your plumbing system. One 50-gallon water heater, for instance, can be served by a 2-gallon expansion tank. If you have more than one heater on the same or connected system you can either have an expansion tank for each heater or a single, larger expansion tank.
#3
08-30-21, 06:11 AM
Thanks, Ben. What air pressure should I set?
When using water the line pressure is 50 psi. When not using water, the line pressure is 70 psi.
When using water the line pressure is 50 psi. When not using water, the line pressure is 70 psi.
#4
09-01-21, 03:58 PM
Preset the expansion tank to approximately the static pressure, 70 PSI. Ever few minutes during the presetting process (using an air pump) open a faucet upstairs so the expansion tank bottoms out at that approx. 70 PSI.
Seventy PSI in from the water main is a little on the high side for home pressure. For this I suggest a 3 or 4 gallon expansion tank.
I estimate that the worst case expansion is one gallon to heat all 50 gallons water up from an incoming 50 degrees F to 120 degrees. When that increase squeezes into the 2 gallon expansion tank the air cushion will have half of the space it occupied before, which means its pressure (and the pressure everywhere else in the system) will double making 140 PSI.
If you preset the expansion tank lower, say, to 50 PSI, the system pressure will still go to 70 PSI when all the faucets are turned off. With the lower preset pressure, water will go into the expansion tank even before the water heater raises its temperature. This leaves less space in the expansion tank for when the water starts expanding from being heated.
Seventy PSI in from the water main is a little on the high side for home pressure. For this I suggest a 3 or 4 gallon expansion tank.
I estimate that the worst case expansion is one gallon to heat all 50 gallons water up from an incoming 50 degrees F to 120 degrees. When that increase squeezes into the 2 gallon expansion tank the air cushion will have half of the space it occupied before, which means its pressure (and the pressure everywhere else in the system) will double making 140 PSI.
If you preset the expansion tank lower, say, to 50 PSI, the system pressure will still go to 70 PSI when all the faucets are turned off. With the lower preset pressure, water will go into the expansion tank even before the water heater raises its temperature. This leaves less space in the expansion tank for when the water starts expanding from being heated.
Wirepuller38,
Zorfdt
voted this post useful.
