Quick Answer:
If your shower is taking longer and longer to get hot, start tracking the delay and flow for a few days. A growing wait time combined with reduced water flow often means mineral buildup or a failing mixing/thermostatic cartridge. Simple checks can narrow the cause, but if the trend continues, call a plumber.
Why This Happens
Two common reasons for an increasing hot-water delay are restrictions in the shower plumbing and a failing cartridge or mixing valve. Mineral deposits (scale) form over time on shower heads, screens and inside cartridges, slowing flow and delaying warm water. A cartridge that is sticking or failing can limit hot water delivery or slow the switch from cold to hot.
Other possibilities include a problem at the water heater (temperature set too low, a partial failure, or a broken dip tube) or a check valve issue in the supply lines. If the problem is only at that shower, it points toward that fixture rather than the heater.
For more on the general symptom and comparisons to other fixtures see Hot water delayed only at shower and for wider troubleshooting about long waits for hot water see Shower takes forever to get hot.
Step-by-Step What to Do
1. Record the delay and flow for one week
- Each time you shower, note the time it takes from opening the hot tap to when the water is hot enough. Use a small notebook or phone timer.
- Also check flow: measure how much water comes from the shower in 15 seconds using a container you know the volume of, or simply note if the spray feels weaker over days.
- Track for at least a week at different times of day. Worsening delay plus declining flow points to buildup or a failing cartridge.
2. Compare other fixtures
- Run hot water from a sink or bathtub. If those take just as long, the issue may be the water heater or main supply. If only the shower is slow, focus on the shower parts.
3. Inspect and clean the shower head
- Remove the shower head or unscrew the faceplate. Look for mineral deposits and rinse or soak parts in a vinegar solution to remove scale.
- Run the shower briefly without the head to see if flow and time to hot improve. If they do, the head or its screen is part of the problem.
4. Check for visible valve issues
- Remove the trim plate to visually inspect the cartridge area if you are comfortable doing so. Look for mineral buildup, corrosion, or a cartridge that does not move smoothly.
- If the cartridge appears seized or degraded, replacement is likely needed. Note brand/model before buying parts.
5. Verify water heater basics
- Check the heater temperature setting (typically 120–125°F / 49–52°C is recommended). Do not increase the temperature beyond safe levels to speed recovery; that creates scald risk.
- If multiple fixtures have reduced hot flow or the heater is older, have the heater inspected for reduced output or a failing dip tube.
6. Decide next steps from your notes
- If delay is steady and flow is fine, the issue may be distance from the heater or normal recovery time.
- If the delay is getting worse and flow is dropping, it points to a developing restriction or failing cartridge—plan for cartridge replacement or professional service.
What Not to Do
- Don’t ignore worsening delay over time—restrictions usually progress and can cause bigger failures later.
- Don’t increase the water heater temperature as a long-term fix—this increases scald risk and can hide an underlying problem.
- Don’t force or hammer on internal valve parts if you’re unsure; you can break components and make repairs harder or more expensive.
When to Call a Professional
Call a plumber if:
- Your week of notes shows an increasing delay and declining flow.
- Cleaning the shower head didn’t help and the cartridge or valve looks seized or damaged.
- You suspect the water heater is failing or multiple fixtures are affected.
A plumber can diagnose cartridge vs. pipe restriction, replace the mixing valve safely, and test the water heater output if needed.
Safety Notes
- Turn off the water supply to the fixture before removing trim or cartridges. If you’re unsure where the shutoff is, shut off the house main and call a plumber.
- Do not raise the water heater temperature above safe limits to try to fix slow hot-up times; scalding is a serious hazard.
- If you find corroded or damaged parts, stop and call a professional rather than attempting risky repairs.
Common Homeowner Questions
- Q: How long should it normally take for a shower to get hot?
A: Typically under a minute in most homes close to the heater; longer if the heater is distant or plumbing loops are long. - Q: Can I fix a failing cartridge myself?
A: A handy homeowner can replace some cartridges, but confirm the model and follow instructions; otherwise hire a plumber. - Q: Will flushing the water heater help a slow-to-heat problem?
A: Flushing can remove sediment that reduces heater efficiency, but it won’t fix a blocked shower valve or cartridge.
For more related articles, see the Shower Takes Too Long to Heat Up hub.