Pressure / Expansion Tank

[Vincent McMahon]

Hi folks, I had a plumber in this morning looking at what it would take to run a dedicated cold line to feed my second floor. Right now it's a single line that feeds both floors. While he was there he said that I should have a small pressure/expansion tank on my water heater. It's a common 40 - 50 gal electric water heater. We don't have a hot water pressure issue.

My question is, - what is the function/purpose of this pressure tank on the water heater, and why would I need it? I don't believe I do, but don't want to overlook anything.

(I will be changing out my well tank soon as the bladder is leaking, and either putting in the same again or going with the Cycle stop system - have not decided yet)

thanks everyone.

 

[John Gayewski]

If your water heater is isolated from your cold water supply line with any type of one way valve then when the water is heated it will expand. When it expands it needs a place to go. Whether you need one or not depends on the components piped into your system.

 

[Sponsor]

 

[LLigetfa]

Unless there is a check valve between the hot water tank and well pressure tank, the well pressure tank will absorb thermal expansion negating the need for an expansion tank.

 

[Vincent McMahon]

If your water heater is isolated from your cold water supply line with any type of one way valve then when the water is heated it will expand. When it expands it needs a place to go. Whether you need one or not depends on the components piped into your system.

Thanks @John Gayewski. My only check valve is before the well tank. The cold water supply line comes from well tank supply line and does not have any valves of any type. SO i guess any expansion is forced back into the well tank?

 

[Vincent McMahon]

Unless there is a check valve between the hot water tank and well pressure tank, the well pressure tank will absorb thermal expansion negating the need for an expansion tank.

Confirmed @LLigetfa.

 

[John Gayewski]

Thanks @John Gayewski. My only check valve is before the well tank. The cold water supply line comes from well tank supply line and does not have any valves of any type. SO i guess any expansion is forced back into the well tank?

Yeah, so you don't need an expansion tank. He probably just got mixed up.

I also think it's incorrect to have one right before the pressure tank. You should have one down in the well at the pump.

 

[LLigetfa]

I also think it's incorrect to have one right before the pressure tank. You should have one down in the well at the pump.

I concur. There should not be any check valve above ground unless a snifter (airmaker) is used in conjunction with a HP tank. In fact it is illegal in many states (rightfully so) as it can facilitate drawing in contaminated surface water.

 

[Vincent McMahon]

I concur. There should not be any check valve above ground unless a snifter (airmaker) is used in conjunction with a HP tank. In fact it is illegal in many states (rightfully so) as it can facilitate drawing in contaminated surface water.

@LLigetfa @John Gayewski That's interesting, this is how it's been installed for 20 years. How does the location of the check valve lead to drawing in surface water? My wellhead/cap is in my driveway, pretty sealed, and 185 ft deep, with a submersible pump. its not in a location that ever would have standing water. Is it something I need to change?

 

[Reach4]

delete

 

[Vincent McMahon]

@Reach4.. Lol.. are you saying it should go?

 

[LLigetfa]

@LLigetfa @John Gayewski That's interesting, this is how it's been installed for 20 years. How does the location of the check valve lead to drawing in surface water? My wellhead/cap is in my driveway, pretty sealed, and 185 ft deep, with a submersible pump. its not in a location that ever would have standing water. Is it something I need to change?

You might have a ticking time bomb. The lower check valve requires pressure against it for it to seal and the topside check valve prevents that. If the lower check doesn't seal, the water column can drop leaving a partial vacuum at the top. When the pump starts, the column slams into the top check creating water hammer which over time can cause a leak to develop in the pipe between the wellhead and the house. Contaminated ground water can then be sucked in through that leak.

 

[Reach4]

@Reach4.. Lol.. are you saying it should go?

No. I had made a comment that I realized had already been covered by previous replies. So I wanted to delete my post, but there is no button to do that. I should probably decided on a different thing to edit my post to, such as "retracted post" .

 

[Vincent McMahon]

No. I had made a comment that I realized had already been covered by previous replies. So I wanted to delete my post, but there is no button to do that. I should probably decided on a different thing to edit my post to, such as "retracted post" .

ha, no worries.. thanks

 

[Vincent McMahon]

You might have a ticking time bomb. The lower check valve requires pressure against it for it to seal and the topside check valve prevents that. If the lower check doesn't seal, the water column can drop leaving a partial vacuum at the top. When the pump starts, the column slams into the top check creating water hammer which over time can cause a leak to develop in the pipe between the wellhead and the house. Contaminated ground water can then be sucked in through that leak.

@LLigetfa ...interesting. I have terrible water hammer. I replaced the check valve by the well, and it eased it a little, but not gone. I also have an issue with my well tank where the bladder is losing pressure. I am considering the CSV solution, as an alternative. But I guess I need to call my well guy to see how they originally installed this and to confirm there is a check valve down below also. He is trying to sell me a 6K new tank install so he may just blame that on the continuous water hammer ....