Plumbing question (water pressure)

[Drummer]

I have a strange problem that recently started in my house. If the hot water tank runs for a long time (such as after a shower)... By the time the hot water tank turns off and is recovered, the COLD water pipes throughout my house have a large amount of pressure built up in the line. If I run any tap on cold it will be super high pressure for 2 or 3 seconds then go back to normal. I'm worried that the built up pressure could cause a line to rupture.

Been in this house for a number of years and the problem has been around for only a few months.

The hot water tank is a traditional style natural gas tank, about 10 years old.
About 6 months ago I replaced the taps in the house (new sinks) and added a water line to the fridge (spliced it off the kitchen sink cold water line). I don't think the renos have caused this issue but it's the weirdest thing. Anyone have any ideas?

[Ducay]

This is expected, as the cold water coming in is heated, it expands and increases pressure in the whole system. Some houses will have backflow preventers or pressure regulators on the main line coming in that prevents this added pressure from going back into the city's lines, and you end up with your case. Specifics of yo uinstallation will impact where and what is over-pressurized (normally the entire system is).

Most installations, this added pressure (a few psi) isn't above the operating pressures, but I agree, it is annoying.

I had the same situation and added a thermal expansion tank to remedy it. Fairly easy install.

Happy to explain further

[Ducay]

Originally Posted by Drummer

About 6 months ago I replaced the taps in the house (new sinks) and added a water line to the fridge (spliced it off the kitchen sink cold water line). I don't think the renos have caused this issue but it's the weirdest thing. Anyone have any ideas?

Further to my other post; I don't think the replacement of taps/fridge would have "caused" this, however, some of the old hardware/runs might have been mitigating the issue so it was less noticeable. (if, per se, one of the old taps would leak when the pressure increased, relieving any built up pressure over, say 100psi).

[Drummer]

Thanks