No Water in Shower but Sinks Work: Cartridge, Diverter, Clog, and Stops

If the bathroom sink (and usually the rest of the house) still has normal pressure, but the shower puts out nothing — or only a trickle — the problem is almost always local to that shower: a clogged head or inlet screen, a stuck or worn cartridge / pressure-balancing unit, a stuck balancing spool, a closed integrated shutoff, or a failed tub/shower diverter. It is rarely the water heater tank or a whole-house clog, because those would hit other fixtures too.

Start here: unscrew the shower head, aim the arm into the tub or a bucket, and turn the valve on. Strong flow at the arm means clean or replace the head. Weak or no flow at the arm means look at stops, diverter, cartridge, and the pressure-balance parts inside the valve — not the kitchen sink.

I’m a homeowner who researches plumbing fixes against manufacturer service docs — not a licensed plumber. The triage below follows OEM guidance from Kohler, Moen, and Delta, plus American Red Cross advice for the frozen-pipe edge case. Brand-specific valve deep-dives belong on their own pages; this guide is the decision tree when sinks are fine and the shower is dead.

This guide was substantially rewritten and re-fact-checked in August 2026.

Key takeaways

• Local vs house-wide: Working sinks rule out “no water to the house.” Focus on the shower head, arm, valve trim, cartridge/PBU/spool, and that branch’s shutoffs.
• Arm test first: Remove the head. If the arm blasts water, descale or replace the head (Delta documents a 50/50 vinegar soak for mineral deposits). If the arm is dead, the valve side is next.
• Pressure-balance valves can shut themselves off: Kohler Rite-Temp units need pressure on both hot and cold at once; one-sided pressure can block the outlet. Moen Posi-Temp / Moentrol issues often trace to a stuck balancing spool or a cartridge that needs replacement and a flushed valve body.
• Check screwdriver stops: Many Kohler Rite-Temp and some Moen valves have integrated stops. Closed stops look like a dead shower with perfect sinks.
• Call a pro for inaccessible frozen pipes, valve bodies that need wall opening, scalding/mixing failures you cannot diagnose safely, or active leaks in the wall.

Quick diagnosis

What you notice	Likely cause	First move
No water at head; strong blast from open shower arm	Clogged nozzles, inlet screen, or flow regulator in the head	Clean screen; 50/50 vinegar soak per brand; or replace head
No/weak water at arm; sinks in same bath fine	Cartridge, PBU, balancing spool, closed stops, or clogged valve ports	Verify stops open; service/replace cartridge or spool; flush valve body
Tub spout works; nothing (or trickle) to shower	Stuck or failed diverter (tub spout or valve-mounted)	Operate/replace diverter; confirm path to shower outlet
Only hot or only cold, or tiny trickle after unused guest bath	Stuck pressure-balance spool / debris in cartridge	Moen: replace Posi-Temp 1222 or free/replace 1423 spool; flush body
Handle turns; silence; stops never touched after remodel	Integrated screwdriver stops left closed	Open stops fully; retest
Cold snap; trickle only; exterior-wall bath	Frozen supply to that branch	Keep faucet open; gentle heat; plumber if inaccessible
Every fixture weak, including sinks	Main, PRV, softener/filter, or municipal supply — not this article’s core case	Check main/stops house-wide; call plumber if pressure is systemically low

Why sinks can work when the shower does not

A shower is its own short plumbing story: dedicated hot and cold drops into a mixing/pressure-balance valve, then an outlet to a shower arm (and often a tub spout with a diverter). The bathroom lavatory usually ties into the same bath branch but through a different faucet. So mineral scale in a shower head, a seized cartridge spool, or a closed stop on the shower valve can leave the sink completely normal.

My honest read of the old “check the water heater / whole-house purifier first” advice: those are poor first stops when sinks still run strong. A dead heater or choked whole-house filter usually shows up at multiple fixtures. Save those for after the arm test and valve checks fail — or when hot is missing everywhere.

Step 1: Prove whether the head is the choke point

1. Shut the shower off. Protect finishes with a cloth and wrench if needed.
2. Unscrew the shower head from the arm. Pull the inlet screen/washer and rinse sediment.
3. Turn the valve on briefly with the arm aimed into the tub or a bucket.

Strong flow at the arm: the supply and valve are delivering water. Clean or replace the head.

• Delta’s mineral-deposit guidance for Touch-Clean® heads is to wipe spray holes to loosen deposits; for harder deposits on non-Touch-Clean heads, soak in a 50/50 white vinegar and water mix, checking periodically and using a toothbrush on remaining scale.
• Large rain faces clog and feel soft for design reasons too — see our rain shower head problems guide rather than repeating that full descaling playbook here.
• Skip “replace the head every 6–8 months” folklore. Replace when cleaning fails, threads are damaged, or the head is cracked — not on a calendar myth.

Weak or no flow at the arm: leave the head off for now and move to the valve side. Do not keep buying shower heads.

Step 2: Tub spout vs shower — check the diverter

On a tub/shower combo, water normally fills the tub until you pull or twist a diverter. If the spout runs full and nothing reaches the arm, or water mostly dumps from the spout when diverted, treat the diverter as suspect: worn seals, mineral lock, or a failed spout-mounted pull-up unit.

Practical checks:

• Confirm the diverter fully engages and holds. A worn spout diverter often returns flow to the spout under pressure.
• With the head removed, divert and watch the arm. Still nothing? The problem may be the valve’s shower outlet port or an internal clog — not just the plastic spout knob.
• Kohler notes that some Rite-Temp setups are not positive shut-off diverters and allow a small permissible spout drip when diverted; simultaneous strong flow from spout and shower usually points to installation or blockage issues, covered in brand valve docs rather than this triage page.

Replacing a spout-mounted diverter is a common DIY. Digging into a valve-body diverter or gated outlet is closer to plumber work if you are not comfortable opening the valve.

Step 3: Open the stops (the “everything looks fine” miss)

Many modern shower valves include integrated shutoffs (often flat-head “screwdriver stops”) on the hot and cold inlets so a tech can service the cartridge without killing the whole house. After a remodel, a forgotten closed stop, or a partial close, the sink can run while the shower valve is starved.

Kohler’s Rite-Temp troubleshooting is explicit: verify stops are open; closed stops block inlet flow. Moen’s No-COLD/HOT FAQ likewise tells you to confirm check stops / shutoffs are fully open before chasing cartridges on ExactTemp and related valves.

After opening stops, retest at the open arm. If flow returns, you just saved a cartridge order.

Step 4: Cartridge, pressure-balancing unit, and balancing spool

This is where “handle turns, nothing happens” usually lives. Brands use different names for related parts:

• Cartridge — the removable mixing/shutoff assembly (e.g., Moen Posi-Temp 1222, Delta MultiChoice cartridges).
• Pressure-balancing unit (PBU) — Kohler Rite-Temp language for the diaphragm/piston assembly that equalizes hot and cold pressure.
• Balancing spool — Moen Moentrol 1423 is a separate front-access spool; on Posi-Temp the spool lives inside the 1222 cartridge.

How pressure balance can create “no water”

These valves are designed to reduce scald risk when someone flushes a toilet mid-shower. The same hardware can refuse to pass water when one inlet is missing, blocked, or far out of balance.

Kohler states that Rite-Temp PBUs need pressure from hot and cold simultaneously; if only one side is applied, the diaphragm can block the outlet. Their docs also call for a minimum of about 45 psi on both supplies. That is why a closed hot stop, a failed water heater on a pressure-balance shower, or a debris-plugged inlet can look like a totally dead shower even though the cold sink still works.

Moen’s tub/shower temperature-troubleshooting FAQ documents the complementary failure mode: debris or a stuck balancing spool so the valve delivers only hot or only cold. For Posi-Temp, they recommend replacing the 1222 cartridge and flushing/cleaning the valve body. For Moentrol, unscrew the brass 1423 spool and confirm the inner spool moves freely; replace if it does not. Separately, Moen’s unused guest-bath Posi-Temp FAQ notes the spool can stick from non-use — replace the cartridge and run the faucet at least once a week to reduce a repeat.

Homeowner-level service pattern (brand manuals win on details)

1. Shut water at the valve stops if present, otherwise at the house main. Open the handle to relieve pressure.
2. Remove trim and extract the cartridge / PBU per the brand sheet. Do not pry plastic cartridges with a screwdriver if the maker says not to (Delta’s MultiChoice instructions use a stem twist-and-pull method).
3. With the cartridge out, briefly flush hot and cold into a bucket to clear loose debris from the valve body — protect the wall cavity from spray.
4. Inspect: mineral crust, torn O-rings, a spool that will not rattle/slide.
5. Delta’s RP46074 cartridge guidance for hard-water areas: with the cartridge in the full-on position, shake vigorously — a rattle means the balance mechanism is free; no rattle means tap the housing, soak 1:1 water and white vinegar about 30 minutes, or replace the cartridge.
6. Kohler’s K-304 Rite-Temp cleaning guide covers mineral deposits causing irregular flow: remove the PBU, wipe the body, and clear the aspirator tube with a vinegar-soaked cotton swab (they caution against other cleaners that can damage the valve). Kohler also notes replacing the PBU for optimal performance when deposits or wear are the issue.
7. Reinstall with correct hot/cold orientation and any rotational limit stop set so cold flows first on a single-handle mix — a burn-safety step Delta emphasizes after cartridge work.

For Kohler-specific symptoms (PBU kits, mixer caps, temperature trim), use our Kohler shower valve troubleshooting page instead of expanding a full brand manual here. Delta cartridge model matching is its own rabbit hole — buy by valve series / RP number, not by “universal” guesses.

Edge cases worth a minute (not your first guess)

Frozen branch piping

If it is bitterly cold, the dead shower is on an exterior wall, and you get only a trickle, suspect ice in that branch. The American Red Cross advises: keep the faucet open; apply gentle heat with a heating pad, hair dryer, space heater kept clear of flammables, or hot towels; never a blowtorch or open flame; call a licensed plumber if you cannot find or reach the freeze. Check other faucets — one freeze often means others are at risk. After thawing, watch for leaks; ice can crack pipes.

Pressure-balance context: a frozen cold line can starve one inlet and make a balance valve shut down or behave oddly even if the hot side is open. That is still a local branch problem, not proof the cartridge is dead — thaw and retest before you order parts.

Shower-only filter, handheld hose, or body-spray loop

A clogged handheld hose, in-line shower filter, or multi-outlet body-spray manifold can kill spray while the sink next to it is fine. Bypass or remove those accessories and retest at the arm before condemning the valve.

Whole-house softener / purifier

Only chase these when multiple fixtures are weak or after the shower arm and valve check out. A softener in bypass that still feeds the house normally is not the shower-only culprit.

What I would not do

• Replace the water heater because one shower is dead and every sink still runs.
• Buy three shower heads before doing the arm test.
• Assume “no water” always means a bad cartridge — closed stops and stuck spools are common and cheaper misses.
• Use open flame to thaw pipes, or leave a space heater unattended against combustibles.
• Ignore scald risk after cartridge work: confirm cold-first / limit-stop settings per the manufacturer.

When to call a licensed plumber

• No accessible shutoffs and you are not comfortable killing the main.
• Valve body corrosion, seized bonnet, or work that needs tile/drywall opened.
• Active leak inside the wall, ceiling stain under a rain panel, or unexplained moisture after you opened the valve.
• Frozen pipe you cannot locate or safely thaw.
• Temperature wildly swings or scalds after you tried a cartridge swap — stop and get help rather than “tuning” by feel.
• Municipal or main-line pressure problems (everything in the house is weak).

How this was researched

This rewrite prioritizes manufacturer troubleshooting for pressure-balance shower valves and shower-head mineral care, plus Red Cross frozen-pipe guidance. It is not a substitute for your exact model’s installation sheet. I have not lab-tested every Kohler, Moen, and Delta valve series; where OEM docs disagree with internet folklore (calendar head replacement, heater-first diagnosis when sinks work), the OEM path wins.

Related guides

• Rain shower head problems — clog vs soft-by-design spray, OEM descaling.
• Kohler shower valve troubleshooting — Rite-Temp / PBU depth without repeating this whole triage.
• Delta shower cartridge troubleshooting — cartridge ID and swap detail.
• Little water coming out of shower head — low flow when some water still arrives.