Shower too hot, not hot enough, or hot and cold reversed
Most single-handle shower temperature problems come down to three things: the cartridge's orientation, its limit stop setting, or a worn pressure-balance part. Each has a specific fix from the valve maker.
Match the problem to the fix
| What happens | Likely cause and what the maker says to do |
|---|---|
| Hot water comes out first, or the handle is backward | Cartridge installed reversed. Moen 1222: rotate the cartridge 180 degrees. Moen 1225: rotate the stem 180 degrees. Delta: seat the cartridge with "hot side" toward the hot supply so cold flows first. |
| Never gets hot enough | Limit stop set too low for the season, or a worn cartridge. Moen Posi-Temp: the handle should reach 9 o'clock at full hot; reset the limit stop if it stops short; if pressure drops as you turn toward hot, replace the 1222. Delta: move the rotational limit stop one notch toward hot and retest. |
| Too hot at full turn | Limit stop set too high. Lower it a notch at a time and check with a thermometer until full hot is 120°F or less. Directions differ: Delta RP46074 clockwise; Delta RP19804 counterclockwise; Moen Posi-Temp clockwise. |
| Temperature surges when a toilet flushes | The pressure-balance part is sticking. Delta: shake the removed cartridge; no rattle means replace it. Moen Moentrol: the separate 1423 balancing spool must move freely. |
| Narrow temperature range, handle turns both ways from off (Moen Posi-Temp) | Handle installed upside down. Remove it, rotate 180 degrees and refit. |
| No warm water, only hot or only cold | Moen: check the handle orientation, then replace the cartridge and flush the valve body. |
Check full hot with a thermometer
Both Moen and Delta tell you to set the limit stop so water at the hottest handle position is 120°F or less (Delta adds: lower if your local code requires). Delta's method: let the water run until it is as hot as it will get, turn the handle to full hot, and hold a thermometer in a plastic tumbler in the stream.
The setting drifts with the seasons: winter supply water is colder, so recheck it then. Delta's instructions also ask the installer to record their name and the date on the caution label.
Why 120°F
The US Consumer Product Safety Commission says most adults suffer third-degree burns from 150°F water in two seconds, 140°F in six seconds and 130°F in thirty seconds, and that even 120°F can burn with five minutes of exposure. Most tap water scald injuries are to young children and older adults. CPSC recommends setting water heaters to 120°F.
Safety: If you cannot bring full hot down to 120°F at the shower valve, have a plumber check the water heater. Water heater work is outside what this site covers.
Limit stop steps by cartridge
Moen 1222 Posi-Temp
Pull the stop out of the key stop, rotate clockwise to a lower notch.
Delta RP46074
Disc or white pull-out stop; clockwise lowers, 4–16°F a notch.
Delta RP19804
One tooth counterclockwise for about each 6°F lower.
Moen 1225 (Moentrol, Standard)
Thermometer check; Moentrol limit stop if the handle stops short.