Bathtub temperature troubleshooting

Bathtub Only Cold Water? Check the Valve and Cartridge First

If the bathtub only gives cold water but the bathroom sink gets hot, keep the first check at the tub valve. Turn the handle toward hot and feel for full travel; an early stop or a stuck pressure-balance cartridge keeps hot water out of the mix.

Run the bathroom sink hot first. If the sink gets hot and the tub stays cold, check handle travel, the limit stop, and the valve cartridge. If more than one fixture stays cold, leave the trim alone and check the hot-water supply.

Use the first checks to sort supply, limit stop, cartridge, and deeper plumbing.

Don’t start with: Do not buy a spout or open the wall first. The visible spout usually only delivers water; the temperature mix happens behind the handle.

Sink gets hotStay with the tub handle, anti-scald stop, and cartridge.

Sink is cold tooLeave the tub trim alone and troubleshoot the hot-water supply first.

Do this first

Run the bathroom sink hot before opening the tub trim.
If hot water is missing at more than one fixture, stop chasing the bathtub valve and check the hot-water supply.
Shut off water before pulling a cartridge, removing retaining clips, or loosening valve parts.
Do not force a stuck cartridge if the valve body moves in the wall.
Stop if you see water behind the trim, inside an access panel, or on the ceiling below.
Hand-test water during every temperature check and keep children away from the tub while testing.

Last reviewed: 2026-07-04

60-second cold-water sorter

Does the bathroom sink get hot?

Yes: stay with the tub valve, handle travel, limit stop, and cartridge. The water heater is less likely.

Are the sink and tub both cold?

Treat it as a hot-water supply problem first. Do not open the tub trim until another fixture gets normal hot water.

Does the handle stop early or only reach lukewarm?

Look behind the handle for an anti-scald limit stop before buying a cartridge.

Does the tub start warm and fade cold?

A sticking pressure-balance cartridge or a plumbing cross-connection moves higher on the list.

Is the cartridge area crusted, wet, or stiff?

Shut water off and inspect carefully. A damaged or scaled cartridge may need replacement.

Did a matched cartridge still leave the tub cold?

Stop guessing at parts. A valve-body, crossover, or supply issue needs a plumber.

Use the sink, handle, and valve clues

A cold-only tub is easier to sort once you compare it with the sink and look behind the handle. The spout is visible, but the mixing failure is usually at the valve.

Bathtub and nearby bathroom sink used to compare hot water for a cold-only tub — Run the bathroom sink hot first and compare it with the tub. Sink hot, tub cold puts the first close look at handle travel, the limit stop, and the valve, not the water heater.

Bathtub handle removed to show the limit stop and valve stem for cold-only water diagnosis — The anti-scald limit stop sits behind the handle on many tub valves. A stop set too cold can block useful hot-water travel without any new part.

Bathtub valve cartridge area exposed during cold-only water troubleshooting — After the sink and limit-stop checks, a stiff or scaled cartridge is the next likely tub-only failure. Stop if the valve body moves or leaks inside the wall.

Before you buy anything

Before buying a cartridge, limit stop, or spout, prove the failure. Compare the sink, handle travel, valve style, and old part shape, then match the exact model or manufacturer part number.

Jump to: Cold-water result map · Tools You May Need · Replacement Parts

What is probably happening

A cold-only bathtub is a mixing problem until another fixture proves otherwise. The first useful split is not the spout; it is whether hot water reaches the bathroom at all.

Hot at the sink and cold at the tub is the clue: hot water reaches the bathroom, so check handle travel and the valve before you blame the water heater.
A limit stop can hold the handle short of the true hot range, especially after trim work or a cautious past adjustment.
A pressure-balance cartridge can stick toward cold when scale, worn seals, or debris keeps the balancing section from moving freely.
Cold at the sink, shower, and tub points away from the bathtub and toward the water heater, a shutoff, or hot-water delivery problem.
A tub that starts warm and fades cold is a good clue to watch for a sticking cartridge or cold water crossing into the hot side elsewhere.

What not to do first

The costly wrong move is replacing the spout because it is the visible outlet. If the tub is cold but the sink is hot, check behind the handle; that valve is where the hot-cold mix is controlled.

Do not buy a bathtub spout for a true cold-only symptom before the valve checks are done.
Do not open the wall because one tub is cold while the bathroom sink has not been tested yet.
Do not pull a cartridge until you know how to shut water off to the valve or the house.
Do not force the handle, trim, or cartridge if the valve body shifts behind the wall.
Do not turn the limit stop hotter and leave it untested; hand-test the water and keep the hottest setting safe for the home.

Cold-water result map

Run the sink on hot, then compare the tub: cold from the start, lukewarm only, or warm then fading. That result tells you whether to check supply, the limit stop, or the cartridge before any part comes off.

Use the bathroom sink because it shares the closest room context with the tub.
Check one more hot fixture only if the sink result is confusing.
Write down whether the tub is cold from the start, lukewarm only, or warm for a short time before it fades.

What you see	What it usually means	Next move
Sink hot, tub cold	Hot water reaches the bathroom; the tub valve is the better target.	Check handle travel, limit stop, and cartridge.
Sink cold, tub cold	The bathtub is probably not the source of the failure.	Troubleshoot the water heater or hot-water supply.
Handle stops before a full hot turn	The anti-scald limit stop may be set too cool or misindexed.	Inspect the stop behind the handle.
Tub warms briefly, then goes cold	The pressure-balance cartridge may be sticking or another fixture may be crossing cold into hot.	Watch other fixtures and inspect the cartridge only after water is shut off.
Matched cartridge did not fix it	The trouble may be in the valve body, piping, or a crossover elsewhere.	Stop part-swapping and call a plumber.

Check the sink before opening the tub

The sink comparison saves the most wasted work. It tells you whether hot water is reaching the room before you disturb trim, old screws, or a cartridge that may be stuck in the wall.

Run the bathroom sink on full hot for 30 to 60 seconds and feel whether it gets normally hot.
Run the bathtub at the same time of day if the symptom comes and goes, then compare the tub temperature to the sink result.
Use a cup and thermometer only if you need a clearer comparison; hand-test first so you do not surprise anyone with hot water.
When the sink is hot and the tub is cold, move to the handle and valve. When both are cold, leave the tub trim alone.
If another nearby single-handle fixture acts odd, test it before taking the tub apart. Cold crossing into hot or the same fade at another fixture can point to a crossover or balancing problem.

Read the handle and limit stop

A limit stop is not a failure by itself. It is a small safety adjustment that can also keep the handle from reaching enough hot water when it is set too conservatively.

Bathtub limit stop exposed behind the handle during cold-water troubleshooting — Make small limit-stop changes and test the water each time. Do not treat the stop like a broken part unless it is cracked, stripped, missing, or will not hold its position.

Turn the handle from cold toward hot and notice whether it stops early, feels blocked, or never reaches a warmer range.
Remove only the handle trim needed to see the stop, and protect the drain so a screw or clip does not disappear.
Move the stop only in small steps if the valve design allows it. Reinstall the handle enough to test after each adjustment.
A limit-stop adjustment that restores normal hot water means no cartridge belongs in the cart yet.
A full handle range with water still cold points more toward the cartridge or valve body.

When the cartridge becomes the lead

Make the valve cartridge the lead only after the sink gets hot and the handle reaches its hot range. If the tub still stays cold or fades cold, shut off water and inspect for scale, torn seals, stiff movement, or a stuck balancing spool.

Shut water off before removing retaining clips or pulling the cartridge.
Look for mineral crust, torn seals, stiff stem movement, a stuck balancing spool, or water leaking around the valve opening.
If the cartridge comes out cleanly and only has light debris, cleaning and reinstalling may be worth one controlled test.
Replace the cartridge when it is scaled, damaged, frozen in one range, or still will not mix hot water after the limit stop is ruled out.
Call a plumber when the cartridge will not move, the valve body shifts, or a matched replacement still leaves the tub cold.

How to Replace a Bathtub Valve Cartridge — Use after the cartridge is the confirmed tub-only failure.
How to Replace a Bathtub Handle Anti-Scald Stop Kit — Use only when the stop is broken or will not hold a safe setting.

Tools You May Need

These tools support careful trim access and diagnosis. Skip internal valve work until you know how the water shuts off.

Screwdriver set

Helps when: Removes handle screws, trim screws, and access-panel fasteners without chewing up the finish.

Skip it when: Skip trim removal if old screws are seized and likely to strip or crack tile.

Compare screwdriver sets on Amazon

Allen key set

Helps when: Fits small handle set screws that hide under the lever or behind a trim plug.

Skip it when: Skip forcing the handle if the set screw is still engaged or rounded out.

Compare allen key sets on Amazon

Inspection flashlight

Helps when: Lights the limit stop, retaining clip, mineral buildup, and any moisture around the valve opening.

Skip it when: Skip working inside the trim opening when you cannot see the clip or cartridge clearly.

Compare inspection flashlights on Amazon

Cartridge puller

Helps when: Helps remove a confirmed stuck cartridge after water is off and the matching puller style is known.

Skip it when: Skip it for a limit-stop adjustment, loose handle, or valve body that moves in the wall.

Compare cartridge pullers on Amazon

Absorbent towels

Helps when: Protects the tub finish, catches trim screws, and gives small drips a place to show up quickly.

Skip it when: Skip using towels as leak control when water is running behind the wall or through the ceiling.

Compare absorbent towels on Amazon

As an Amazon Associate I earn from qualifying purchases. Repair Riot may earn a commission at no extra cost to you.

Replacement Parts

Parts make sense only after the checks point there. Match the old part, valve brand, stem shape, retaining clip, and trim style before ordering.

Tub/shower valve cartridge

Helps when: Buy this when the sink gets hot, handle travel is normal, and the old cartridge is stiff, scaled, or damaged.

Skip it when: Skip it when hot water is missing at the sink too or the limit stop has not been checked.

Compare tub/shower valve cartridges on Amazon

Pressure-balance cartridge

Helps when: Use this for valves where the pressure-balance cartridge is the matching temperature-control part.

Skip it when: Skip it if your valve uses separate hot and cold stems or a different cartridge style.

Compare pressure-balance cartridges on Amazon

Anti-scald limit stop kit

Helps when: Buy this if the stop is cracked, stripped, missing, or will not hold a safe setting after adjustment.

Skip it when: Skip it when the stop simply needed adjustment and still locks securely behind the handle.

Compare anti-scald limit stop kits on Amazon

Bathtub spout

Helps when: Compare this only after the valve makes hot water and the spout still leaks, restricts flow, or the diverter fails.

Skip it when: Skip it for a true cold-only tub before the valve and cartridge checks are done.

Compare bathtub spouts on Amazon

As an Amazon Associate I earn from qualifying purchases. Repair Riot may earn a commission at no extra cost to you.

FAQ

Why does my bathtub only have cold water when the sink gets hot?

That points to the bathtub valve, not the water heater. Start with handle travel and the anti-scald limit stop, then inspect the cartridge if the tub still will not mix hot water.

Can the anti-scald stop make a bathtub run cold?

Yes. If the stop is set too cool or indexed wrong, the handle may never reach the hot side far enough. Adjust it in small steps and hand-test the water after each change.

Can a bathtub spout cause only cold water?

Usually no. If the sink gets hot and the tub stays cold, check behind the handle before buying a spout. Leaks, weak flow, or diverter trouble point at the spout; temperature mix points back to the valve.

How do I know if the bathtub cartridge is bad?

The valve cartridge moves up the list after the sink gets hot, the handle turns through its full range, and the tub still stays cold or fades cold. Shut off water, then inspect for stiff stem movement, mineral scale, damaged seals, or a stuck pressure-balance section.

Why does the tub start warm and then turn cold?

A sticking pressure-balance cartridge can do that. A cross-connection elsewhere can also push cold water into the hot side, especially if other fixtures act strange at the same time.

Should I replace the whole bathtub faucet if the tub only runs cold?

Not first. Run the sink hot, check the limit stop, and inspect the cartridge. If the handle has full travel and the matched cartridge still leaves the tub cold, then the valve body or piping may need a plumber.

Can I clean a bathtub faucet cartridge instead of replacing it?

Sometimes. Light debris may rinse out, but a worn, scaled, cracked, or sticking cartridge is better replaced with the exact match for the valve.

When should I call a plumber for a cold-only bathtub?

Call when you cannot shut off water, the cartridge is seized, the valve body moves, you find leakage behind the wall, or a correctly matched cartridge still does not restore hot water.

How this page was built

Repair Riot rebuilt this page around the sink comparison, bathtub valve behavior, anti-scald limit stops, cartridge fit, and the point where a cold tub becomes a plumber call. Source links support water-heater separation, scald caution, and leak-stop boundaries; the diagnostic sequence is original guidance.

U.S. DOE water heating guide — supports separating bathtub-only temperature trouble from whole-home water-heater issues.
CPSC tap water scald guidance — supports hand-testing and keeping hot-water safety in view when adjusting temperature.
EPA WaterSense Fix a Leak Week — supports fixing fixture leaks and stopping water before small problems waste water or damage finishes.