Rinna Tankless Water Heater: Pressure Issues & Expansion Tank Leak

[MethodicalMind]

Background:
My house is a new build, currently two years old. Last year, I measured the PSI from the expansion tank without any issues. Recently, out of curiosity, I tried to get a PSI reading again but this time a small amount of a sticky, clear fluid (possibly sealant) slowly leaked from the valve.

Pressure Regulator Valve (PRV) Status
I haven't experienced any issues with the PRV discharging.

Previous Plumbing Issue & Pressure Readings
During the first year, while the house was still under warranty, a plumber came to investigate a low-pitched screeching sound coming from the shower head. He said it was due to low water pressure and subsequently increased the pressure using the PRV on the main line that's located in the garage. While he believed the issue was resolved, I remained somewhat unconvinced; i was still able to hear the pitched sound.

During his pressure testing we noticed a discrepancy in pressure readings: the pressure gauge on the main water line inside the garage read 100 PSI (static), while the hose bib at the front of the house read 80 PSI. The plumber did not explain this difference, nor why he relied on the hose bib reading for adjustment. Needless to say he adjusted the hose bib to 80 PSI and therefore the gauge on the main water line always read 100 PSI.

Possible Expansion Tank Issue & Closed System
My home likely has a closed water system due to the presence of a backflow preventer valve associated with the in-house sprinkler and irrigation systems. This is likely why the expansion tank was installed with the tankless water heater.

Questions Implied

• Is the leaking fluid from the Schrader valve a definite sign that the expansion tank has failed? If so, why might have that happened within 2 years?
• Why the 20 PSI discrepancy in static pressure between the gauge on the main water line and the hose bib?
  • How do i know which pressure setting to trust?

Link of the high pitched sound of the shower head:

 

[CT-18]

Is the 100 PSI reading before the PRV in the garage. You should have consistent pressure on the house downstream of the PRV. You should only be getting air or water at the Schrader valve unless maybe something is breaking down inside the expansion tank. Testing at a hose bibb is a good spot to screw on the gauge unless you have a older style laundry tub faucet.

 

[GReynolds929]

Regarding the showerhead squeal, if it is a tub/shower faucet and the tub spout has a diverter that you pull to turn on the shower, the squealing is usually the tub spout washer not fully sealing. Replace the spout and see if the squeal persists.

Pressure gauge can vary in their accuracy and go bad regularly. I would check pressure at the water heater cold service valve with a new hose bib gauge and see what it says. If it is different from the house valve I would replace the house valve.

On a good thermal expansion tank properly precharged, you should only get air when depressing the Schrader valve. I would suspect that yours is failing. The tank should be precharged with air to the house pressure. If that didn't happen when pressure was increased that can lead to premature failure.

The galvanized pipe on the tankless water heater is not a good idea. It will release bits of rust and corrosion that will at minimum clog the inlet filter. Any galvanized piping should be replaced with brass, copper, or PEX.

Tankless water heaters need to be descaled and flushed annually at minimum. If this has not been done it should be done soon.

Most residential reducing valves have a max pressure of 75-80 psi, yours should have a tag stating what it's max regulated pressure is. If your pressure is higher than that the valve has failed. Also to note it looks like you have fire sprinklers, that usually means they want a minimum of 70 psi to ensure adequate flow from the heads. Code max pressure is 80 psi in a residential dwelling.

 

[Rossando]

G-Reynolds hit it on the nose. nasty pipework installed on the wrong kind of system it should be brass or copper when dealing with water pipes to prevent future issues.
Descale unit once a year and use a gauge on the water heater service port(check cold first then hot side when in operation) and see if the pressure rises when in use. sounds like a bad PRV valve but check the shower head as well. Those rubber gaskets get squirrely if its worn down or not in one piece replace it with a new. lastly those flow restrictors in the shower head might be plugged give it a good blow or baking soda and vinegar bath if its junked up inside. I would just buy a new one but time is money and whichever one you have more of, either time or money.

 

[MethodicalMind]

Is the 100 PSI reading before the PRV in the garage. You should have consistent pressure on the house downstream of the PRV. You should only be getting air or water at the Schrader valve unless maybe something is breaking down inside the expansion tank. Testing at a hose bibb is a good spot to screw on the gauge unless you have a older style laundry tub faucet.

"Is the 100 PSI reading before the PRV in the garage." - I don't know. Water flow direction is from down and up in the OP photo. I assume the reading is after the PRV.

"You should have consistent pressure on the house downstream of the PRV." - How do I measure pressure downstream of the PRV?

 

[MethodicalMind]

Regarding the showerhead squeal, if it is a tub/shower faucet and the tub spout has a diverter that you pull to turn on the shower, the squealing is usually the tub spout washer not fully sealing. Replace the spout and see if the squeal persists.

Pressure gauge can vary in their accuracy and go bad regularly. I would check pressure at the water heater cold service valve with a new hose bib gauge and see what it says. If it is different from the house valve I would replace the house valve.

On a good thermal expansion tank properly precharged, you should only get air when depressing the Schrader valve. I would suspect that yours is failing. The tank should be precharged with air to the house pressure. If that didn't happen when pressure was increased that can lead to premature failure.

The galvanized pipe on the tankless water heater is not a good idea. It will release bits of rust and corrosion that will at minimum clog the inlet filter. Any galvanized piping should be replaced with brass, copper, or PEX.

Tankless water heaters need to be descaled and flushed annually at minimum. If this has not been done it should be done soon.

Most residential reducing valves have a max pressure of 75-80 psi, yours should have a tag stating what it's max regulated pressure is. If your pressure is higher than that the valve has failed. Also to note it looks like you have fire sprinklers, that usually means they want a minimum of 70 psi to ensure adequate flow from the heads. Code max pressure is 80 psi in a residential dwelling.

- It's a standalone shower without a tub
- "I would check pressure at the water heater cold service valve with a new hose bib gauge and see what it says." - I don't understand. Where would i attach the pressure reading gauge at the water heater cold service line?
- "The galvanized pipe on the tankless water heater is not a good idea" - are you referring to the circled pipe that attaches to the expansion tank? If so, is that a disassembled pipe that can be removed a proper one installed?
- "Most residential reducing valves have a max pressure of 75-80 psi, yours should have a tag stating what it's max regulated pressure is. If your pressure is higher than that the valve has failed" - Ok, but not if the plumber increased it to 100 PSI (in order to achieve 80 PSI at the hose bib) and chose to follow the hose bib instead of the gauge at the main water line.

 

[GReynolds929]

Like Rossando said the washer at the showerhead could be an issue, or debris in the showerhead. Have you tried a different showerhead?

Underneath the water heater there is a brass set of valves on the inlet and outlet, should have blue handles and red handles. There is a hose thread connection on each valve to allow the heater to be descaled. Attach a pressure that screws onto a hose bib at one of the water heater connections and open the corresponding valve. I circled the locations in red.

Yes the pipes circled in blue should be replaced. They are threaded pipes.

Even if the adjustment bolt is screwed in all the way the regulator will not allow the pressure to exceed its maximum regulated pressure which is usually 75 psi. If the pressure is higher than that the PRV is not working. The plumber can not just turn up the pressure higher than the device allows. What does the tag on the PRV say it's pressure range is?

 

[MethodicalMind]

Like Rossando said the washer at the showerhead could be an issue, or debris in the showerhead. Have you tried a different showerhead?

Underneath the water heater there is a brass set of valves on the inlet and outlet, should have blue handles and red handles. There is a hose thread connection on each valve to allow the heater to be descaled. Attach a pressure that screws onto a hose bib at one of the water heater connections and open the corresponding valve. I circled the locations in red.

Yes the pipes circled in blue should be replaced. They are threaded pipes.

Even if the adjustment bolt is screwed in all the way the regulator will not allow the pressure to exceed its maximum regulated pressure which is usually 75 psi. If the pressure is higher than that the PRV is not working. The plumber can not just turn up the pressure higher than the device allows. What does the tag on the PRV say it's pressure range is?

It wasn't just one shower head, it was all three in the house. I'm curious if this might even be normal with the Tankless water heaters since water is heated on demand...if the changes in water temperature in real time are contributing to changes in pressure and therefore sound. I donno, maybe that doesn't make sense.
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What are the pipes called that connect the cold supply line to the thermal expansion tank? Do you have links to home depot website?
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Did what you said. Attached the pressure gauge to the cold supply hose thread and got 80 PSI. Take a look at the quick video. I think my pressure gauge at the water line is likely defective. Should I have checked the pressure at the hot one as well?

 

[Rossando]

A plumber cannot turn this up to 100 psi if the device is not rated to go that high. It would be a range. What I see most often are the zurn Wilkins 3/4" set range is usually between 50-75. If it is higher it is broken and has failed. And yes I have seen these "plumbers" with 10 years experience break brand new ones messing with them because there just installers(monkeys with tools).

 

[MethodicalMind]

A plumber cannot turn this up to 100 psi if the device is not rated to go that high. It would be a range. What I see most often are the zurn Wilkins 3/4" set range is usually between 50-75. If it is higher it is broken and has failed. And yes I have seen these "plumbers" with 10 years experience break brand new ones messing with them because there just installers(monkeys with tools).

I think the gauge on the water line is faulty. I'm not getting above 80 PSI on the cold supply line at the water heater or any of the hose bibs outside.