What Gets Decided Before Anything Is Opened

Like for like, or a different type

Replacing a Type P with a Type P is the simple case. Moving to a thermostatic valve is a different product with different behavior and usually a different price, and it may need different plumbing behind it.

Decide which before the wall is open, because that is when the option is still free.

Whether the trim can stay

Trim and valve are matched. Changing the valve usually means changing the trim, which means a new escutcheon that may not cover the same footprint on the tile.

Ask whether the new plate covers the old one’s opening. It is a boring question and it is the one that produces unwelcome surprises.

Where the water gets turned off

Some installations have stops at the valve itself, reachable through the trim. Most do not, and the supply comes off for the whole property while the work happens.

Worth knowing in advance if anybody in the house needs water during the day.

And the limit stop, at the end

A new valve arrives with a limit stop that has to be set. ASSE states it must be set by the installer to the desired temperature, and that the maximum safe temperature is mandated by the local code.

Ask for it explicitly as part of the work, and ask what it was set to. A valve replaced without that step is a valve that can go as hot as whatever reaches it.

Source: ASSE International, Adjustment of Automatic Compensating Valves to Prevent Potential Scald Hazards.

Further reading

• The limit stop
• Behind the wall
• Cost