The most common shower problems are low pressure, a clogged showerhead, a drip after shut-off, temperature swings, a stuck diverter, a slow drain, and leaks behind the wall or under the pan. Most trace to mineral scale, a worn cartridge or hair in the drain. Heads, cartridges and drains are DIY; hidden leaks need a plumber.
Quick reference: problem, cause, fix
Use this table to match what you're seeing to the likely cause, then jump to the section below for the details and the deeper guide.
| Problem | Likely cause | Fix | DIY or call? |
|---|---|---|---|
| Weak spray, other fixtures fine | Scaled showerhead or flow restrictor | Soak and clean the head | DIY |
| Weak spray everywhere | Whole-house pressure or regulator | Test house pressure | Test is DIY; regulator is a call |
| Spray shoots sideways, nozzles blocked | Mineral scale in the nozzles | Vinegar soak, brush nozzles | DIY |
| Drip from the head after shut-off | Worn cartridge seals | Replace the cartridge | DIY for most |
| Leak where the head meets the arm | Loose connection or worn washer | Thread tape, new washer | DIY |
| Hot and cold swings | Sticking pressure-balance cartridge or spool, water heater | Cartridge, spool or heater service | DIY cartridge; heater may be a call |
| Water stays in the tub spout | Worn or scaled diverter | New spout or diverter cartridge | Usually DIY |
| Slow or standing water | Hair and soap in the strainer or trap | Clean strainer, zip tool, plunger | DIY |
| Water comes up the shower when a toilet flushes | Main sewer line blockage | Stop using water, call | Call |
| Stain or damp wall behind the valve | Valve body or connection leak | Open wall, repair valve | Call |
| Water outside the shower, loose tile, damp floor | Failed pan or liner | Water test, rebuild pan | Call |
Here's the pattern: anything you can reach from the front of the shower is usually yours to fix. Anything behind the tile isn't.
Water flow and temperature problems
These are the problems you feel on your skin. They're also the ones most often caused by Phoenix water. The city's 2025 water quality report lists hardness of 10 to 17.6 grains per gallon and says hard water can cause scaling in pipes and water heaters, and on fixtures such as faucets and showerheads.
### Low water pressure
A weak shower is usually a showerhead problem, not a plumbing problem. Moen's troubleshooting for its PosiTemp valve gives the cleanest test: take off the showerhead and run water through the shower arm. If you're getting good flow through the arm, Moen says to clean the showerhead to remove any debris and replace it if necessary. If flow is still weak with the head off, the cartridge is the next suspect.
Keep expectations realistic. EPA WaterSense notes that standard showerheads use 2.5 gallons per minute, while WaterSense labeled models must use no more than 2.0 gpm. A new efficient head will feel different from a decades-old one, and that isn't a defect. If every faucet in the house is weak, the showerhead isn't the problem at all. Our guide to why your shower pressure is low walks through the whole-house versus one-fixture test.
### Clogged showerhead
Mineral scale builds up inside the nozzles until spray goes sideways or stops in spots. Soaking the head in white vinegar and scrubbing the nozzles clears most of it. For removable heads, a soak is best. For fixed heads, a bag of vinegar tied around the head works. The step-by-step is in how to clean a clogged showerhead. Repeat it every few months in hard water. Simple as that.
### Dripping showerhead
A showerhead that keeps dripping after you shut the handle off usually has worn seals in the valve cartridge. Water is sneaking past the cartridge, not the head. EPA WaterSense says a showerhead leaking at 10 drips per minute wastes more than 500 gallons per year.
There are two different drips to tell apart:
- Drip from the nozzles with the valve off. That's the cartridge. Replacing it is a manageable DIY job with the right part; our guide on how to replace a shower cartridge covers Moen, Delta and Kohler. For Moen's PosiTemp 1222, Moen recommends cleaning and flushing the valve body before the new cartridge goes in.
- Leak where the head screws onto the arm. That's the connection. EPA WaterSense says some of these can be fixed by making sure the connection is tight and using pipe tape, and that it's a good idea to check the washer or "o" ring inside the showerhead too.
For valve leaks in showers that drip when not in use, EPA WaterSense suggests contacting an experienced handyperson or licensed plumber. That's fair if you don't know your valve brand or can't shut off the water.
### Temperature swings
A brief dip when someone flushes is normal. Real hot or cold blasts are not. The usual cause is a pressure-balance cartridge or spool that no longer slides freely. Moen describes the cause of a shower stuck on only hot or only cold as "Debris or an obstruction in the balancing spool is causing it not to move freely within its housing." The fix is a new cartridge and a flushed valve body, or on some Moen valves a new balancing spool.
Water heater problems and tankless flow limits can cause swings too. We cover the full diagnosis in why your shower temperature keeps changing. If the shower runs lukewarm while the sinks run hot, see no hot water in the shower only.
A quick safety note: the 2024 International Plumbing Code, Section 412.3, requires shower and tub-shower valves to be pressure-balancing, thermostatic or a combination, with a limit that keeps the water at or below 120°F. If yours scalds, fix it before someone gets hurt.
### Diverter won't switch to the showerhead
On a tub-shower, the diverter sends water up to the head instead of out the spout. When it wears or scales, water keeps pouring from the spout, or splits between both. A lift-gate diverter lives inside the tub spout, so the fix is a new spout. A diverter built into the valve needs its own cartridge. Our page on a shower diverter that isn't working shows how to tell which one you have.
Drain problems
Drains are the other big category, and the cause is almost always what goes down them.
### Slow or clogged shower drain
Hair bound up in soap scum is the classic clog. It collects at the strainer and in the trap just below. The International Plumbing Code, Section 421.3, requires shower waste outlets of at least 1 1/2 inches with removable strainers at least 3 inches across. That strainer is your first cleanout point. Pull or unscrew it, clear the hair, then use a barbed zip tool or a plunger on the trap. Hot water after the clog is out helps flush what's left. Our guide to a bathtub that won't drain covers each stopper type, and most of the steps apply to a stall shower too.
Skip harsh drain chemicals. The bathtub guide explains why they're the wrong tool for a hair clog.
### Water backing up into the shower
If water rises in the shower when a toilet flushes or the washer drains, that's not a shower problem. The shower is often the lowest drain in the house, so a blocked main sewer line shows up there first. Stop running water and call for help. A plunger won't reach a main-line clog. Details are in why water comes up in the shower when you flush.
Leaks you can't see
Hidden leaks are the costly ones, because the water goes into framing, subfloor and ceilings before you notice.
### Shower valve leaking behind the wall
Warning signs include a damp or stained wall or ceiling near the shower, peeling paint, a musty smell, or water sounds with everything off. A worn cartridge can still be the cause, but a leak at a soldered joint or a cracked valve body means opening the wall or working through an access panel. See how to tell if your shower valve is leaking behind the wall. If you suspect this, shut off the water to the shower and keep it off until it's checked.
### Failed shower pan or liner
In a tiled shower, the tile isn't the waterproofing. A liner under the mortar bed is. The 2024 IPC, Section 421.5.2, requires shower floors (other than prefabricated receptors) to be lined and made watertight. The liner has to turn up the walls at least 2 inches above the finished threshold, slope 1/4 inch per foot toward the drain, and be tested before tile goes on. When a liner fails, you see water outside the shower, loose or cracked tile near the curb, or damp flooring in the next room. A pan rebuild means removing tile, so it's a call, not a weekend project. Our page on shower pan liner code goes deeper on slope, curb and the water test.
### What you can do today
Check caulk and grout lines where tile meets the tub or pan, and recaulk any gaps. Look under the shower from the room or ceiling below if you can. Run the shower for ten minutes, then check for damp spots outside the enclosure. These checks don't fix a failed pan or valve, but they tell you whether you have one.
That's the list. Most shower problems are a scaled part or a hair clog, and you can handle those with basic tools. When water is getting where it shouldn't, behind the wall or under the floor, bring in a licensed plumber before the damage spreads.
HQ Plumbing & Air is licensed and insured, offers 24/7 emergency service, and gives upfront pricing and free estimates on shower repairs.
Leaks under the pan usually trace to the install, so see how to install a shower pan.