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Our boiler and hot water tank have been blowing water for a while. The hot water tank much longer than the boiler.
When it first started, the hot water tank would drip water after water was used. Hubby did replace the pressure relief valve but didn't resolve the problem.
At some point, it started BLOWING water after water was used. A big huge gush we could hear when we weren't in the basement.
The boiler company came last week to do maintenance. Hubby told him about the hot water tank blowing. (Unfortunately, hubby only mentioned the boiler was leaking, not blowing.) The technician told hubby to take the hot water exapansion tank to the gas station and set it to match the house pressure to resolve that problem.
The hot water tank has not blown any water since he changed the pressure to 70. (Prior, it blew every single time the water was used anywhere in the house.) Hubby says that it needs to match the house pressure because too much pressure pushing against the expansion tank causes the expansion tank to blow because diaphram inside the expansion tank can't hold against the high pressure.
Everywhere I have read on the internet since the technician came here says that the hot water expansion tank pressure needs to be changed to match the house pressure. There are youtube videos on how to change the pre-charge of an expansion tank. Just because the factor pre pressurized it at 40 doesn't mean it's the right pressure.
This youtube video dude explains that the pressure needs to match the pressure inside the house and shows how to change the pressure:
Somehwhat related and unrelated to this thread, there is a similar issue with the boiler. Since hubby only told the technician the boiler was leaking (instead of blowing), the technician told hubby to replace the relief valve on the boiler. (This hasn't been don yet.) I asked hubby why the expansion tank on the boiler didn't need to be increased to the house pressure too. It just didn't make sense tome that they both shouldn't need to be set the same. For some crazy reason, hubby thinks it's different because the systems are separate. Even though the hot water tank and the boiler are separate, they aren't separate from the house pressure IMO, but hubby thinks a regulator that is prior to the boiler lowers the water pressure before it gets to the boiler.
On Monday, I will be calling the boiler company to come back for the boiler, but the hot water tank issues are definitely resolved.
Wow, I never knew that. So, I guess I need to kick up the pressure to whatever my house water pressure is. I have several 12Volt tire compressors. Should be easy.
Edit: Just did it. I measured my house water pressure at 45. I shut off the water, opened the sink and measured the tank. It was about 37. So I used a compressor and added some pressure to the tank so it is now 45.
Wow, I never knew that. So, I guess I need to kick up the pressure to whatever my house water pressure is. I have several 12Volt tire compressors. Should be easy.
Edit: Just did it. I measured my house water pressure at 45. I shut off the water, opened the sink and measured the tank. It was about 37. So I used a compressor and added some pressure to the tank so it is now 45.
We didn't know for a long time ourselves. I posted this thread in April 2001 saying that it was happening for about a year. That means almost 2-1/2 years before the mystery was solved.
A previous post says house pressure shouldn't be 120 psi. Hubby was talking to the neighbor and coincidentally his house pressure is 120 psi. He says it makes for great showers. He lives just across the street. I'm jealous, but I can't imagine how much water my water tank would have been blowing if our pressure had been 120 psi.
Glad you were able to do it so easily easy. 37 to 45 isn't too much of a pressure difference, but having the pressure properly balanced will help prevent any future problems.
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