Well and Hot Water Expansion Tank

[Rotaris]

Yes the pressure goes to 60psi.
I had the expansion tank set at 40psi for 5 years, it just always banged and creaked at lowered pressure in the line. So I though it should be set a little higher, that is when the brain damage started!
I thought by setting the expansion tank to 59psi it would get rid of this, which it did. Except now the pressure climbs to like 70 after using hot water. I just can not comprehend why?
The expansion tank should be taking excess pressure. Not going above ???????

 

[Reach4]

I thought by setting the expansion tank to 59psi it would get rid of this, which it did. Except now the pressure climbs to like 70 after using hot water. I just can not comprehend why?
The expansion tank should be taking excess pressure. Not going above ???????

When the water enters, it takes space. The air on the other side of the diaphragm compresses. Pressure goes up. That's the way it works.

If your thermal expansion tank were twice as big, the pressure would rise half as much.

 

[Sponsor]

 

[Rotaris]

4.8 Gallon tank, seems plenty, I mean plenty? Guess I just try running lower pressure.

 

[Jadnashua]

A well will have a pressure tank to store water so that the pump doesn't have to run every time you draw a little water. That pressure tank would be set to a pound or two below the minimum your pressure switch provides. That will ensure that at the minimum pressure before the pump turns on, there's still a little water in the pressure tank, otherwise, it could run dry as the pump turns on.

Water doesn't compress. If you have a check valve between the pressure tank and your water heater, you still have a closed system. If your check valve is before the pressure tank...that's more normal, then you normally don't need an expansion tank as heated water will expand and push back into the storage tank. But, you don't want water to back flow through a water softener, so you may have a check valve protecting it, thus, an expansion tank for water heating would be required.

If you say have a 40/60 pressure switch for your well, then you'd set the expansion tank to 60-psi. If the ET precharge pressure was at 60-psi after using a bunch of hot water, as the water heater reheated the water, it would expand, and that expansion would push back into the ET. If the ET is sized properly, and precharged properly, the actual system pressure won't go up much. If the ET is undersized, the pressure will, and could spike if it was really too small. Since the air will compress, the volume of the water will cause the air pressure to rise, but much more slowly. Since you may only get a few cups expansion from a nearly drained WH from cold to normal temperature, you're not compressing the air in an adequately sized ET for the pressure to rise much. Ten pounds sounds like either it's not precharged properly, or it's undersized.

 

[Valveman]

The well pump pressure tank will double as an expansion tank, as long as there are no other check valves after the pressure tank. A 4.5 gallon size pressure/expansion tank will hold about 1/2 gallon of water before the pressure gets up to 70 PSI. I don't think the hot water would expand by 1/2 gallon, so the pressure should not increase much at all.

 

[Rotaris]

A well will have a pressure tank to store water so that the pump doesn't have to run every time you draw a little water. That pressure tank would be set to a pound or two below the minimum your pressure switch provides. That will ensure that at the minimum pressure before the pump turns on, there's still a little water in the pressure tank, otherwise, it could run dry as the pump turns on.

Water doesn't compress. If you have a check valve between the pressure tank and your water heater, you still have a closed system. If your check valve is before the pressure tank...that's more normal, then you normally don't need an expansion tank as heated water will expand and push back into the storage tank. But, you don't want water to back flow through a water softener, so you may have a check valve protecting it, thus, an expansion tank for water heating would be required.

If you say have a 40/60 pressure switch for your well, then you'd set the expansion tank to 60-psi. If the ET precharge pressure was at 60-psi after using a bunch of hot water, as the water heater reheated the water, it would expand, and that expansion would push back into the ET. If the ET is sized properly, and precharged properly, the actual system pressure won't go up much. If the ET is undersized, the pressure will, and could spike if it was really too small. Since the air will compress, the volume of the water will cause the air pressure to rise, but much more slowly. Since you may only get a few cups expansion from a nearly drained WH from cold to normal temperature, you're not compressing the air in an adequately sized ET for the pressure to rise much. Ten pounds sounds like either it's not precharged properly, or it's undersized.

Thanks, like stated above 4.8 gallon, maybe to small? 40 gallson water heater, but a lot of line full of water.
Check valve is in clack head after pressure tank so closed loop.
Just want to thank everyone for help. Need time to play with it!

 

[Rotaris]

The well pump pressure tank will double as an expansion tank, as long as there are no other check valves after the pressure tank. A 4.5 gallon size pressure/expansion tank will hold about 1/2 gallon of water before the pressure gets up to 70 PSI. I don't think the hot water would expand by 1/2 gallon, so the pressure should not increase much at all.

Yep check valve in Clack ws1 four button, after pressure tank, thus reason for expansion tank...........head scratcher for sure

 

[Reach4]

Thanks, like stated above 4.8 gallon, maybe to small? 40 gallson water heater, but a lot of line full of water.
Check valve is in clack head after pressure tank so closed loop.
Just want to thank everyone for help. Need time to play with it!

You could add another pressure tank or extra thermal expansion tank downstream of the check valve, such as at the output of the softener. While you should not have to worry about a rise to 80 or 100, you do. So it could be worthwhile to you. Maybe a 20 to 32 gallon pressure tank. This will also cause your pump to run less.

Another alternative is a system, with water sensors on the floor, that shuts off your water in the case of a pipe burst.

 

[LLigetfa]

You could add another pressure tank

No, do not install a second pressure tank far away from the first tank. Depending on pump GPM output and friction loss between tanks, it can cause unintended consequences with the pressure switch.

 

[Reach4]

No, do not install a second pressure tank far away from the first tank. Depending on pump GPM output and friction loss between tanks, it can cause unintended consequences with the pressure switch.

He has a check valve after his pressure switch and pressure tank, so I think no problem interaction.

 

[Rotaris]

I have lived with the creaks and groans for 5 years on the expansion tank. It has always worked to limit excess pressure in system. I am just trying to optimize. Worst case I go back to 40 psi pre-charge. No chance of a second tank, too much crap already in the water system.

 

[Reach4]

I have lived with the creaks and groans for 5 years on the expansion tank. It has always worked to limit excess pressure in system. I am just trying to optimize. Worst case I go back to 40 psi pre-charge. No chance of a second tank, too much crap already in the water system.

Making no change other than reducing the precharge of the thermal expansion tank to 40 psi will increase the peak pressure that your pipes experience.

 

[LLigetfa]

He has a check valve after his pressure switch and pressure tank, so I think no problem interaction.

I disagree. The second tank could fill at a slower rate than the primary one so the pressure switch may shut the pump off based on what the pressure is at the switch and one or both tanks might be at a pressure lower than the cut-off. This may cause the pump to turn back on worst case, or turn on sooner negating the benefit of the second tank to reduce pump cycles.

 

[Reach4]

I disagree.

I agree with that.

 

[LLigetfa]

I agree with that.

So we agree to disagree?
A hot water expansion tank air precharge is normally set to the cut-off pressure setting of the pump so it would be empty when the pump is running so would not negatively interact with the pressure switch.

 

[Reach4]

No chance of a second tank, too much crap already in the water system.

Rotaris, ignore the discussion below. I can also imagine another way around this, but it would involve more stuff that may rise to your definition of crap-- but not a new tank.

So we agree to disagree?

Yes.

A hot water expansion tank air precharge is normally set to the cut-off pressure setting of the pump so it would be empty when the pump is running so would not negatively interact with the pressure switch.

Suppose pressure switch is 40/60. Suppose both tanks are 32 gallon. Suppose the check valve has a 2 psi drop. Suppose the pressure drop from the check valve to the second pressure tank is 5 psi max. Suppose the well pump supplies between 7 and 11 gpm.

Whether the second pressure tank has 36 psi precharge, or 58 psi precharge, I cannot picture an oscillation/interaction condition causing the pump to run more often. Take the check valve out of the picture, maybe. But not with the check valve.

 

[LLigetfa]

Way too much supposing... One has to also factor friction loss that the piping and water conditioning adds. As also mentioned, the GPM refill rate of the pump is also a factor since friction loss is on a curve dependent on GPM of flow.

Simple rule... don't have two pressure tanks far apart or even a single tank far from the pressure switch.

 

[Rotaris]

So we agree to disagree?
A hot water expansion tank air precharge is normally set to the cut-off pressure setting of the pump so it would be empty when the pump is running so would not negatively interact with the pressure switch.

Just to be clear, check valve is in Iron filter/Clack head..........after pressure Tank/switch.Expansion tank is installed after The Iron filter

 

[Rotaris]

Way too much supposing... One has to also factor friction loss that the piping and water conditioning adds. As also mentioned, the GPM refill rate of the pump is also a factor since friction loss is on a curve dependent on GPM of flow.

Simple rule... don't have two pressure tanks far apart or even a single tank far from the pressure switch.

Is this not the case with a lot of expansion tanks installed after well systems,just thinking out loud?

 

[LLigetfa]

Is this not the case with a lot of expansion tanks installed after well systems,just thinking out loud?

No. Expansion tanks have higher precharge than pressure tanks. I addressed that in post https://terrylove.com/forums/index....water-expansion-tank.22790/page-2#post-658870