Hot water looses pressure

[Johnny B-FUN]

Hello,

My 2008 189FBS hot water starts with high pressure and but drops to minimal flow in about 5 seconds. It happens all faucets. The water is hot.

I have flushed the hot water tank, replaced the check valve, replaced the anode (because it was time) and pushed air through the lines without any changes or obvious blockages.

If left alone the pressure will build back up.

Looking for other possible troubleshooting steps.

Thanks,
John

 

[Rocky Mtn marmot]

Did you check the inbound cold water line, sounds like a severe blockgage or a defective valve that only opens a tiny bit. Some water heaters trap a small amount of air and this pressurizes the tank just enough to have good hot water flow for a few seconds in spite of there being very little cold water coming into the water heater.

 

[Johnny B-FUN]

Hello. Thanks for your response. Cold water runs without an issue and the tank seems to fill in a normal amount of time. When heating I can hear the pressure valve whining for about 5 seconds after about 20 min.

 

[Rocky Mtn marmot]

The pressure relief valve shouldn't make any noise. I would replace it. Does the pump run as soon as you open a hot water faucet like it would when opening a cold water faucet, unless of course if you have a captive air tank. Do you have the same problem if the water heater is turned off and cold? Try temporarily removing the check valve.

 

[Johnny B-FUN]

Hello. Thanks for your response. Cold water runs without an issue and the tank seems to fill in a normal amount of time. When heating I can hear the pressure valve whining for about 5 after about 20 min.

The pressure relief valve shouldn't make any noise. I would replace it. Does the pump run as soon as you open a hot water faucet like it would when opening a cold water faucet, unless of course if you have a captive air tank. Do you have the same problem if the water heater is turned off and cold? Try temporarily removing the check valve.

Thanks for the advice. You have given me a couple of things to try. I have only been testing connected to a water supply and I have not tested on the pump. My next step was going to be to install a check valve with the components removed (creating an open nipple). I will post back in a few days. Glad I reached out to the chat…

 

[Johnny B-FUN]

The pressure relief valve shouldn't make any noise. I would replace it. Does the pump run as soon as you open a hot water faucet like it would when opening a cold water faucet, unless of course if you have a captive air tank. Do you have the same problem if the water heater is turned off and cold? Try temporarily removing the check valve.

Got back to this today. I removed the check valve and it was marginally better but pressure did drop off. Will order a pressure valve as well as try it with cold water only.