Shower valves and trim: what has to match

The rough-in valve

The rough-in valve is installed in the wall before tile goes on. It controls temperature and flow. Because it's buried behind tile, choose it first and choose carefully.

Pressure-balance or thermostatic

• Pressure-balance valves keep the hot-and-cold mix steady when someone flushes a toilet or runs a tap. One handle controls both temperature and flow.
• Thermostatic valves hold a set temperature and usually have separate volume controls. They suit showers with several outlets, such as a rain head and a handshower.

Both types should meet the anti-scald standard ASSE 1016 or an equivalent listing.

Trim compatibility

Trim (the handle, plate and spout) only fits valves from the same manufacturer, and often only a specific valve series. Before ordering, confirm:

• The valve model in your wall, if you're replacing trim only.
• That the trim and valve are from the same compatible family.
• The number of outlets the valve supports.

Wall depth and tile

The valve must sit at the correct depth for your wall and tile thickness. Most valves have a plaster guard showing the acceptable range. Tell your plumber the total thickness of board plus tile.

Diverters and outlets

A diverter sends water to different outlets: rain head, wall head, handshower or tub spout. Some systems run outlets one at a time; others can share. Check how many you want to use at once.

What to include in a quote request

• Pressure-balance or thermostatic.
• Each outlet you want.
• Wall construction and tile thickness.
• The finish, and whether the valve is already installed.