Quick Answer:
If sinks deliver hot water but the shower only gets lukewarm, the shower’s anti-scald limiter or the pressure-balance cartridge is probably restricting hot flow. First locate and carefully adjust the anti-scald limit stop per the manufacturer and retest the shower. Also confirm the showerhead restrictor isn’t reducing flow enough to upset the mixing. If this started after a recent plumbing change, check related items like No hot water after filter install before calling someone.
Why This Happens
- Most modern showers use a pressure-balancing or thermostatic valve with an anti-scald limiter. That limiter reduces maximum hot water to prevent burns; if set too low, the shower will stay lukewarm while other fixtures are hot.
- Low flow from a clogged showerhead or a flow-restricting insert can change the pressure balance and reduce hot water through the valve.
- Changes to supply pressure or recent work on pipes can shift how the valve mixes hot and cold. If this followed a pressure change, see Shower cold after pressure change for troubleshooting ideas.
Step-by-Step What to Do
1. Confirm the pattern
- Turn on a hot sink faucet and verify full hot temperature. Then run the shower and set it to the hottest setting you normally use.
- Note whether the shower can reach true hot at any handle position or if it tops out lukewarm only in the shower.
2. Locate the anti-scald limit stop
- Remove the trim/handle as the manufacturer instructs to expose the valve cartridge and the anti-scald stop or limit screw.
- Look for a small plastic or metal stop on the cartridge or valve body; the manual will show its exact location and the safe adjustment direction.
3. Adjust the anti-scald limit stop and retest
- Make small adjustments (a quarter-turn or a notch at a time) toward allowing more hot water, following the manufacturer’s directions. Reinstall the handle temporarily and test water temperature after each small change.
- Test with your hand first, then confirm with a thermometer if you want precision. Stop if the water feels uncomfortably hot and back off a bit.
- Reinstall the trim properly when finished and verify operation through the full range of the handle.
4. Check the showerhead and flow restrictor
- Unscrew the showerhead and look for a plastic flow-restricting disc or screen. Clean any debris and confirm the restrictor isn’t clogged or excessively low-flow.
- Temporarily run the shower without the head to see if increased flow lets the valve reach hotter temperatures. If temperature improves, replace or clean the restrictor and retest.
5. Inspect the cartridge and valve
- If adjusting the limit stop and fixing flow don’t help, the pressure-balancing cartridge may be worn or stuck. Look for debris or corrosion around the cartridge and consider replacing the cartridge per manufacturer instructions.
- If you see visible damage or the cartridge is seized, stop and consider a professional replacement unless you are comfortable with valve repairs.
6. Final checks
- After any change, test other fixtures to ensure the overall hot water supply and the water heater are working normally.
- Return the anti-scald setting to a safe maximum (commonly around 120°F / 49°C) if you adjusted it higher to troubleshoot.
What Not to Do
- Don’t remove anti-scald limits entirely—adjust them safely following the manufacturer’s guidance so the shower still limits scalding risk.
- Don’t force or break valve parts to get more hot water; that can cause leaks or permanent damage.
- If you can’t verify settings, a plumber is appropriate—don’t guess at permanent changes to the valve or plumbing.
When to Call a Professional
- If you can’t access the limit stop or cartridge without specialized tools or removing the valve body.
- If the cartridge is corroded, damaged, or stuck and won’t move after cleaning.
- If adjusting the limiter or fixing flow doesn’t fix the temperature and you’re unsure about valve replacement or reassembly.
Safety Notes
- Always follow the valve manufacturer’s instructions when removing trim or adjusting settings.
- Test water temperature cautiously after adjustments to avoid scalds. Use short tests with your hand before staying under the water.
- Keep the maximum safe temperature in mind—setting the limit too high increases scald risk for children and older adults.
Common Homeowner Questions
- Why are sinks hot but the shower is lukewarm?
Most likely the shower’s anti-scald limiter or pressure-balance valve is limiting hot flow or the showerhead flow is too low, upsetting the mix. - Can I adjust the anti-scald stop myself?
Yes if the trim and instructions are accessible and you follow the manufacturer’s steps; make small adjustments and retest carefully. - Will cleaning the showerhead help?
Sometimes—removing the restrictor or cleaning debris can restore flow and fix mixing issues, but check the limiter if problems persist.
FAQs
- How do I know the anti-scald stop is the issue?
Adjusting it slightly and seeing a temperature change at the shower usually confirms it. - Will turning the stop fully open damage anything?
Don’t fully remove or force it; follow manufacturer limits to avoid scald risk and valve damage. - Is this an emergency?
No—lukewarm showers are uncomfortable but not an immediate hazard; work methodically and call a pro if unsure.
For more related articles, see the No Hot Water at Shower but Everywhere Else hub.