Our building in Richmond Hill, Ontario, Canada has a regulator / backflow preventer that is permanently set to 175 PSI.

Our water heaters all have T&P valves that are 150 PSI and are residential Space Saver type. This was built by very large construction company (Urbacon).

Why would they use residential water heaters instead of commercial ones?

Why would they have T&P valves that are below the building water pressure?

The T&P on 4 water heaters are always leaking (with no drains provided) until we replaced one T&P with a 175 PSI and now no more leaks.

If you had an expansion tank wouldn't it just fill up until it could fill anymore then the T&P would start leaking again?

We had a few plumbers that still can't figure out why the hot water tanks keep leaking without changing the whole building water regulator / backflow preventer to a lower one if they even make one.

Just trying to make some logic of why they would build that way. Thanks for your info.

Here is a pic of the water pressure that we measured which seems to sit about 80 PSI but can get up to 180 or 190 PSI.

[mega.nz]

Y'all need a better dual or perhaps triple stage regulator to prevent 'creep' under no or low flow conditions.



Y'all 'should' have a pressure compression (expansion) tank sized for the entire building.



Y'all need better plumbers on site.

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

DITTO