Only the bathtub is cold
The bathroom sink or another nearby faucet gets properly hot, but the tub stays cold or barely warm.
Start here: This points first to the bathtub valve trim, anti-scald stop, or bathtub faucet cartridge.
Bathtub temperature problem
Bathtub Only Cold Water
Direct answer: If the bathtub only gives cold water but nearby sinks still get hot, the trouble is usually in the tub valve, not the water heater. The most common causes are a stuck bathtub faucet cartridge, a mis-set anti-scald limit stop, or a pressure-balance valve that is hung up on the cold side.
Most likely: Start by checking whether the bathroom sink gets normal hot water. If it does, focus on the bathtub handle, trim setting, and cartridge before you assume a bigger plumbing problem.
A tub that stays cold can look like a water-heater problem when it really is one fixture refusing to mix hot water. Reality check: if every fixture is cold, the bathtub is probably not the main problem. Common wrong move: replacing the spout because it is the visible part, even though the temperature control usually lives back in the bathtub valve cartridge.
Don’t start with: Do not start by buying a new bathtub faucet or tearing into the wall. A lot of these turn out to be a limit-stop setting or a cartridge that can be confirmed first.
If the sink is hot tooStop chasing the tub valve and check the house hot-water supply first.
If only the tub is coldGo straight to the handle, anti-scald setting, and bathtub faucet cartridge.
Last reviewed: 2026-04-05
What this usually looks like
Tub and sink are both cold
You cannot get hot water anywhere nearby, or hot water is weak throughout the house.
Start here: Check the water heater or whole-house hot-water issue before opening the bathtub trim.
Bathtub starts warm then turns cold
You get a little warm water for a moment, then the tub drops to cold while flow continues.
Start here: Look closely at a sticking pressure-balance bathtub cartridge or a cross-connection issue elsewhere in the plumbing.
Handle turns but temperature barely changes
The tub handle moves normally, but from full cold to full hot there is little or no temperature change.
Start here: Suspect a misadjusted anti-scald limit stop first, then a failed bathtub faucet cartridge.
Most likely causes
1. Bathtub faucet cartridge stuck or failed
This is the most common tub-only cause. Mineral buildup, worn seals, or a jammed pressure-balance section can block hot water from mixing in.
Quick check: Run the bathroom sink hot first. If the sink gets hot but the tub does not, remove the tub handle trim and inspect the cartridge area next.
2. Anti-scald limit stop set too cold
Many tub valves have a temperature limit stop behind the handle. If it was set too conservatively or slipped during a past repair, the handle never reaches the true hot range.
Quick check: With the water on, move the handle fully to hot. If it stops early and never reaches a hotter position, check the limit stop behind the trim.
3. Hot-water supply issue affecting more than the tub
If the sink, shower, and tub are all cold or only lukewarm, the tub valve is probably innocent. The hot-water source or distribution is the better first target.
Quick check: Test the nearest sink and one other hot fixture in the house before taking the tub apart.
4. Cross-connection or balancing problem in the plumbing
Less common, but a bad mixing valve or failed cartridge at another fixture can let cold water push into the hot side, especially when the tub is running.
Quick check: If the tub starts warm then fades cold, and other fixtures act odd too, shut off nearby single-handle fixtures one at a time and retest.
Step-by-step fix
Step 1: Confirm whether this is a tub-only problem or a house hot-water problem
This separates the most common lookalike right away. You do not want to open the tub trim if the water heater is the real issue.
- Run the bathroom sink on full hot for at least 30 seconds.
- Check one more hot fixture in another room, like a kitchen sink.
- Notice whether hot water is missing everywhere, weak everywhere, or missing only at the bathtub.
- If the tub has a separate shower function, test both tub spout and showerhead if safe to do so.
Next move: If other fixtures get normally hot and only the bathtub stays cold, keep going on this page. If hot water is missing or weak throughout the house, stop here and troubleshoot the hot-water supply instead of the tub.
What to conclude: A bathtub-only failure usually lives in the bathtub valve trim or cartridge. A whole-house failure points away from the tub.
Stop if:
- Hot water is missing at every fixture in the house.
- You hear banging, see leaks, or find water coming through an access panel or ceiling while testing.
Step 2: Check the handle travel and anti-scald limit stop
A mis-set limit stop is a common, low-cost fix and easier than replacing parts. It also explains tubs that only get lukewarm even though the sink gets hot.
- Turn off the tub water.
- Remove the bathtub handle carefully and set the screws aside.
- Look behind the handle for a plastic or notched temperature limit stop.
- Compare the handle's hot-side travel to the stop position and adjust it a little warmer if the design allows.
- Reinstall the handle enough to test, then run the tub and check temperature again.
Next move: If the tub now reaches normal hot temperature, the problem was the anti-scald setting and no replacement part is needed. If the handle now has full travel but the tub is still cold or barely warm, move on to the cartridge check.
What to conclude: A limit stop that was set too cold blocks the handle before the valve can open the hot side fully.
Step 3: Look for signs the bathtub faucet cartridge is stuck on the cold side
Once the limit stop is ruled out, the cartridge becomes the strongest tub-only suspect. Physical clues here are usually better than guessing.
- Shut off water to the tub valve if there are local stops or shut off the house water if needed.
- Remove the handle and trim far enough to access the bathtub valve cartridge area.
- Check for white mineral crust, corrosion, stiff handle movement, or a cartridge stem that does not return smoothly.
- If the cartridge can be removed without damaging the valve body, inspect for torn seals, debris, or a stuck balancing spool.
- If the cartridge is heavily scaled, damaged, or frozen in one temperature range, plan on replacing it rather than forcing it back into service.
Next move: If cleaning light debris and reinstalling restores hot water, verify stable temperature through a full tub run. If the cartridge is damaged, badly scaled, or the tub still runs cold after reassembly, replace the bathtub faucet cartridge with the correct fit.
Step 4: Rule out a tub spout issue only if the valve is confirmed to be working
The spout is not the usual cause of cold-only water, but a diverter or internal restriction can confuse the symptoms if flow changes oddly between tub and shower.
- With the trim back together enough to run water, compare temperature at the tub spout and at the shower function if your tub has one.
- Watch for weak flow, sputtering, or a diverter that partially sends water upward when it should stay at the spout.
- If the valve now mixes correctly but the spout leaks, dribbles, or behaves erratically, inspect the bathtub spout separately.
- Replace the bathtub spout only if the temperature issue is solved at the valve but the spout still has its own flow or diverter problem.
Next move: If both tub and shower now get hot after valve work, the spout was not the main issue. If the valve still will not deliver hot water, go back to the cartridge branch or call a plumber for valve-body diagnosis.
Step 5: Finish with the right repair or escalate cleanly
By now you should know whether this is a simple adjustment, a cartridge replacement, or a deeper plumbing issue that should not be guessed at.
- If the anti-scald stop fixed the problem, set the hottest safe temperature you want and reinstall all trim securely.
- If the bathtub faucet cartridge was clearly failed, replace it with the correct match for your valve and retest hot-water range.
- After reassembly, run the tub for several minutes and confirm the handle moves smoothly from cold to hot without sudden temperature swings.
- If the tub still goes cold while other fixtures behave strangely, suspect a cross-connection or deeper valve-body issue and call a plumber.
- If opening the trim revealed leakage behind the wall or through an access panel, address that leak before regular use.
A good result: You should have steady hot water at the bathtub, normal handle travel, and no seepage around the trim or access area.
If not: If a confirmed cartridge replacement does not restore hot water, the problem is likely beyond a simple fixture part and needs professional diagnosis.
What to conclude: A successful fix is usually either a corrected limit stop or a restored bathtub faucet cartridge. Persistent cold after that points to a less common supply or valve-body problem.
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FAQ
Why does my bathtub only have cold water when the sink gets hot?
That usually means the hot-water source is fine and the problem is inside the bathtub valve. The most common causes are a stuck bathtub faucet cartridge or an anti-scald limit stop set too cold.
Can a bathtub spout cause only cold water?
Usually no. A bathtub spout can cause leaking, poor flow, or diverter trouble, but true cold-only water is more often a valve or cartridge problem upstream.
What is the anti-scald limit stop on a bathtub?
It is a small adjustment behind the handle that limits how far the handle can turn toward hot. If it is set too conservatively, the tub may never reach normal hot temperature even though hot water is available.
Why does the tub start warm and then turn cold?
A sticking pressure-balance section in the bathtub faucet cartridge is a common cause. A plumbing cross-connection elsewhere can also push cold water into the hot side and create the same symptom.
Should I replace the whole bathtub faucet if the tub only runs cold?
Not first. Start with the sink comparison, then check the anti-scald setting and cartridge. Replacing the whole faucet or opening the wall is usually unnecessary unless the valve body itself is damaged.
Can I clean a bathtub faucet cartridge instead of replacing it?
Sometimes, if the issue is light debris or mild mineral buildup. But if the cartridge is worn, heavily scaled, or still sticks after cleaning, replacement is the better fix.