Why won't my shower get hot?
Updated August 2026
When one shower runs lukewarm or cold while the sink and every other tap still deliver hot water, the culprit is nearly always a worn pressure-balancing (mixing) cartridge inside the shower valve, stuck so it can no longer swing to the hot side. The cartridge is a $20–80 part and the most common fix for a shower that lost its heat. First confirm the rest of the house still gets hot, then work down the causes below. A pro cartridge swap runs $150–300; doing it yourself costs only the part.
Safety first: the anti-scald limit stop exists to keep water from leaving the valve hot enough to burn. If you reset it to gain more hot water, do not open it all the way: water above 120F scalds a child in seconds, and most codes cap shower output near 120F. Set the heater to 120F and adjust the limit so full hot lands warm, not dangerous.
Causes, most likely first
| Cause | How likely | The fix | Typical cost |
|---|---|---|---|
| Worn pressure-balancing cartridge | Most common | Shut the water at the valve stops or the main, pull the handle and cartridge, and drop in a matching replacement. Kits are sold by valve brand and model. | $20–80 part, $150–300 installed |
| Anti-scald limit set too low | Common | Most single-handle valves have a rotational limit stop or hot-limit ring. Reset it so the handle can reach fuller hot without hitting the stop. | Free adjustment |
| Water heater underperforming | Common | If every hot tap is weak, the heater is at fault: a tripped element, a low thermostat, or a tank overdue for a flush. Check the heater, not the shower. | $0–300 |
| Crossed hot and cold lines | Occasional | A recent valve or plumbing job can reverse the supplies, or let cold bleed into the hot side through a failed cartridge, diluting the mix. | $150–350 |
| Sediment clogging the cartridge | Occasional | Grit from a water-heater flush or a pipe repair lodges in the cartridge ports. Cleaning or replacing the cartridge clears it. | $20–120 |
Check these first
- Run the bathroom sink and a hot tap elsewhere. If those get hot and only the shower stays cold, the shower valve, not the heater, is the problem.
- Hold the handle at full hot for a full minute. A cartridge only partly stuck sometimes creeps warmer, which still points at replacing it.
- Look for a limit-stop ring under the handle trim. If someone recently reset the valve, the anti-scald stop may simply be capping the hot side.
- Note any recent work: a new water heater, a pipe repair, or a valve rebuild often stirs sediment or crosses the lines.
- Read the valve brand stamped on the trim or cartridge so you buy the exact replacement, since cartridges are not universal.
Prevent it next time
Shower cartridges are wear parts: the rubber seals harden and the plastic body scores over years of use, faster in hard water. A cartridge that starts drifting on temperature or dripping is telling you it is near the end. Replacing it at the first sign, rather than waiting for full failure, is a 30-minute job. If your shower valve is past its 20 to 30-year life or the body itself is corroded, our repair-or-replace guide walks the math, and the shower-valve explainer covers the parts. If the heat comes and goes instead, see why a shower swings hot and cold.
When to call a pro
Call a plumber when the valve has no accessible stops and you must shut the main, when the cartridge is seized and will not pull with a puller, or when the valve body itself leaks behind the wall. A cartridge swap runs $150–300 with a pro, and a full valve replacement that requires opening the wall runs $350–800 or more. If every hot fixture in the house is weak, skip the shower entirely and have the water heater diagnosed first.
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Stop chasing symptoms, free for 30 daysFrequently asked questions
Why is only my shower cold when everything else is hot?
Because a single-handle shower has its own mixing cartridge that blends hot and cold right at the valve, and that part fails independently of your plumbing and heater. When the cartridge wears out or clogs, it can stick toward cold even though scalding water sits ready in the hot supply. Sinks and tubs with separate handles do not rely on the same part, which is why they stay hot. Replacing the $20–80 cartridge almost always brings the heat back.
Can a bad cartridge make the shower too hot instead of cold?
Yes. The same pressure-balancing cartridge that can stick cold can also fail toward hot, or stop balancing entirely, so the water spikes when someone flushes a toilet or runs the kitchen sink. A cartridge that no longer holds a steady temperature is worn out whichever way it drifts. Replace it, then set the water heater to 120F and adjust the anti-scald limit so a future failure can never send burning water to the head.
How long does it take to replace a shower cartridge?
For a confident DIYer, about 30 to 60 minutes once you have the matching cartridge in hand. The work is shutting off the water, removing the handle and trim, pulling the retaining clip, extracting the old cartridge (a $15 puller helps when it is stuck), and reversing the steps. The hardest part is usually identifying the exact brand and model so the replacement seats. A plumber does the same job in under an hour and charges $150–300 including the part.