A shower that has lost pressure almost always has a blockage somewhere between the valve and the spray face, and the blockages are easy to find because you can test at each point. Work through the list in order. Most people are done at step 1 or 2.
Before you start. No need to shut off the water for this one; the valve stays closed while you work on the head, arm, or spout. You will need a towel to protect the finish, slip-joint pliers or an adjustable wrench, and a roll of plumber’s tape (thin white thread tape, about $2). If anything is corroded and will not loosen with moderate force, stop and see when to call a plumber. New to this? Start here explains the parts and tools in plain language.
Looking for the valve behind the wall instead (the handle that controls temperature)? That repair depends on the brand. See how to find your brand and the brand page for your shower.
Find where the water is being slowed
- Look at the spray face. If some nozzles spray sideways, dribble, or are crusted white, the head is scaled. Go to cleaning the shower head. That fixes most weak showers.
- Unscrew the head from the arm (turn the nut counterclockwise while holding the arm with your other hand; wrap a cloth around the arm so pliers do not scratch it). Inside the nut you will find a rubber washer and a small screen. Rinse the screen. If it is packed with grit or scale, that was the problem. Delta’s instructions call this the debris screen.
- With the head off, turn the shower on briefly. If the water comes out of the bare arm with good force, everything behind the wall is fine and the problem is in the head. Clean it, or replace it if cleaning does not help.
- If the flow from the bare arm is also weak, check the shutoff valves. On a tub and shower there are usually none in the wall, but some houses have stops in an access panel behind the tub or in the basement ceiling. Make sure both are fully open.
- If both the tub spout and the shower are weak, or only the hot or only the cold is weak, the pressure balance cartridge in the valve is clogged or worn. Moen’s own troubleshooting for its Posi-Temp valve ends here with replacing the 1222 cartridge. That repair is brand specific; see your brand page. The same logic applies to Delta Monitor, Kohler Rite-Temp, and the others.
- If every fixture in the house is weak, it is not the shower. Check the main shutoff is fully open, then the pressure regulator if the house has one, then the water heater inlet if only hot is weak everywhere.
About the flow restrictor
Every shower head sold in the United States since 1994 is limited to 2.5 gallons per minute by federal law, and many are now 1.75 or 2.0 gpm. The limit is set by a small plastic disc inside the head. Delta states that it does not recommend removing the restrictor and that doing so voids the warranty; Kohler’s installation guide says not to attempt to remove the flow control. A head that has always been weak in a house with normal pressure is working as designed, and the fix is a different head rather than modifying this one. A head that used to be fine and is now weak has a clog, not a restrictor problem.
Parts
- Delta: how to clean a shower head
- Moen: low flow troubleshooting for Posi-Temp showers
- Replacement shower heads at Home Depot
Faucet Answers is reader supported. Some links to retailers and manufacturers are affiliate links, and purchases made through them may earn a small commission at no extra cost to you. See the affiliate disclosure.