Water heater expansion tank leaking

[DFBonnett]

Daughter's house. Two years old on 50 gal gas AO Smith. End "button" shows red indicating needing replacement and dripping from there about four drops per minute. House pressure measures 90#. No pressure reducing valve. Previous heater did not have an expansion tank and there were no issues with the TPR valve. When it was being installed, the plumber told me that the TPRs are "different" now and expansion tanks are needed on all water heaters. I had a Smith installed in my house since with no tank and no issues. Was the plumber pumping sunshine?
Can I just shut off the supply and install a new expansion tank pre-charged at 40# or must I increase the pressure? Since there is no pressure reducing valve, can I remove the tank and install a 3/4" brass plug since the system was fine before ?

 

[Twowaxhack]

House pressure should be 80 or less.

Install the tank and increase the charge to 90 psi before you turn the water on.

 

[DFBonnett]

Since nothing has changed since the previous water heater which had no expansion tank, is the expansion tank necessary? The only thing that changed was the size of the WH.

 

[DFBonnett]

House pressure should be 80 or less.

Install the tank and increase the charge to 90 psi before you turn the water on.

Local water supplier, in essence , told me if I don't like it to go piss up a rope and that they are not liable.

 

[DFBonnett]

The question that remains unanswered is if the expansion tank is really necessary on an open system which has no pressure reducing valve.

 

[Twowaxhack]

If the system isn’t closed then it’ll only expand to the current water pressure then it’ll push out the main. So the answer is no.

Are you a professional plumber ?

 

[DFBonnett]

No, not professional, barely an amateur. I think I'll remove the tank, plug the fitting, then see what happens. My best guess is nothing since there were no issues before.

 

[Twowaxhack]

No, not professional, barely an amateur.

I’ll help anyway I can

 

[wpns]

The question that remains unanswered is if the expansion tank is really necessary on an open system which has no pressure reducing valve.

If there's no check valve (usually a pressure reducing valve from the city water main, but I had an iron filter with a check valve, so it's likely that water softeners and other water treatment devices could have a check valve) that would trap the water in your house (and raise the pressure when the water heater increases in temperature), then you don't need the expansion tank. You'll know soon enough if your pressure valve pops off or if the water pressure coming out of the taps is really high occasionally after the heater runs.

 

[wpns]

Install the tank and increase the charge to 90 psi before you turn the water on.

I think I'm about to learn something. Well pressure tanks want the precharge set to a little below the lowest water pressure (the cut-in on the switch), do hot water heater expansion tanks want the recharge set to higher than the expected maximum pressure?

 

[BlueSkyHigh]

No, not professional, barely an amateur. I think I'll remove the tank, plug the fitting, then see what happens. My best guess is nothing since there were no issues before.

I asked the same thing of the plumber that installed my latest hot water heater. He said that the local code requires it and, no, he could not leave it out of the system. Of course he may just have been needing to sell the expansion tank but I chose not to disagree.

 

[wpns]

I suspect a lot of this 'the code requires it' is that it's easier to say 'must have an expansion tank' than it is to say 'must have an expansion tank when there's check valve in the system, which could be from any one of these potential devices {list of devices} and maybe others, but be prepared to prove to the inspector that your device does not have a check valve, and if you add a device later and you don't have an expansion tank then you are required to install one", and then write into the Water Filter Code that a hot water heater expansion tank is required, yaddah, yaddah, yaddah.

 

[Hamberg]

Pretty sure Burlington county follows the IPC - here is the "Code Requirement":

607.3 Thermal expansion control. Where a storage water heater is supplied with cold water that passes through a check valve, pressure reducing valve or backflow preventer, a thermal expansion control device shall be connected to the water heater cold water supply pipe at a point that is downstream of
all check valves, pressure reducing valves and backflow preventers.

Thermal expansion tanks shall be sized in accordance with the tank manufacturer’s instructions and shall be sized such that the pressure in the water distribution system shall not exceed that required by Section 604.8.

 

[Twowaxhack]

I think I'm about to learn something. Well pressure tanks want the precharge set to a little below the lowest water pressure (the cut-in on the switch), do hot water heater expansion tanks want the recharge set to higher than the expected maximum pressure?

In the context of this thread the OP said his water pressure is 90 psi. So I said set the tank to 90 psi.

We’re not required to have expansion control unless the system is closed.

We prove the system isn’t closed by placing a gauge and firing the heater for the inspector.

 

[wpns]

OP said his water pressure is 90 psi. So I said set the tank to 90 psi.

So for hot water heater expansion tanks the precharge should be set to the house pressure? What if that pressure varies, should it be the high or low pressure?
No longer an issue for me, just curious.
Thanks!

 

[Twowaxhack]

So for hot water heater expansion tanks the precharge should be set to the house pressure? What if that pressure varies, should it be the high or low pressure?
No longer an issue for me, just curious.
Thanks!

It should be set higher at the max pressure the system will see. So if the pressure varies, go with the higher number.

If that number is higher than 80 psi then a PRV should be installed.

If you set the expansion tank higher than needed it reduces the capacity of the tank.

I often set my tanks at 80 psi as we rarely have water pressure above 80 psi in my area. A few hoods do, I know my area.

If a customer’s water pressure is 70 psi and I set his tank to 80 psi, the system will build to 80 psi then the tank will control it.

If I set the same tank to 100 psi the system would build pressure then control it at 100 psi. But the tank capacity would be reduced a little. Water temp and size of the water heater all play a role in how much expansion the tank can control.

If you set the tank pressure to 45 psi and the water pressure to the home was 75 psi……same result, reduced expansion tank capacity. The tank would fill mostly with water……

 

[DFBonnett]

Many thanks to all who responded. My daughter has decided to contact the plumber who installed the WH, advise him that the house pressure is 90# per my request, and let him decide upon a solution. Those of you with grown kids know that sometimes you just have shut your mouth and let them do what they do.

 

[wpns]

/*
If you set the tank pressure to 45 psi and the water pressure to the home was 75 psi……same result, reduced expansion tank capacity.
*/
How much expansion capacity do you need?

 

[Twowaxhack]

/*
If you set the tank pressure to 45 psi and the water pressure to the home was 75 psi……same result, reduced expansion tank capacity.
*/
How much expansion capacity do you need?

Enough to keep the pressure below 80 psi.

Incoming water temp and final water temp are factors. How much water you’re heating also is a factor.

 

[DFBonnett]

So... finally my daughter calls the company that installed the water heater. The guy comes and admits that they likely didn't pump the tank bladder up to line pressure initially and that since there is no pressure reducing valve in place, the tank might not be needed in the first place. Claims that AO Smith requires the tank for warranty purposes. Installs new tank with bladder pumped up to 80#, 10# over tested line pressure, leaves a fat bill which my daughter pays. Now she agrees that if this tank fails I can put a plug in place of the tank.