Quick Answer:
If your shower started fluctuating after a remodel, don’t panic. The most common causes are a partially closed valve stop or remodel debris clogging the showerhead or cartridge, or a replacement valve that lacks a working pressure-balance or thermostatic element. Start with simple checks you can do without special tools; if you can’t confirm the valve setup or the problem persists, call a plumber.
Why This Happens
- Remodel work often leaves solder, pipe scale, drywall dust or sealant debris in lines. That debris can partially block the showerhead or the valve cartridge and cause rapid temperature swings.
- New valves sometimes get fitted without their internal safety parts reinstalled, or a different valve type was used. A missing or faulty pressure-balance or thermostatic element will let hot or cold pressure changes pass straight to the shower outlet.
- During a remodel, valve stops (the small shut-off handles behind the wall or in an access box) can be left partly closed for testing or protection. Partially closed stops change flow balance and cause instability.
- Other household changes (like adding a filter or new appliances) can change water pressure intermittently; for related scenarios see Temperature swings after filter install and for time-based patterns see Shower temperature varies by time of day.
Step-by-Step What to Do
1. Check the easy visible items first
- Turn the shower on and run it for a minute. Note whether fluctuations are sudden (pressure crosses) or gradual (slow drift).
- Remove the showerhead and run the water directly from the arm for a short test. If the flow is steady without the head, the head is likely clogged with debris from the remodel.
2. Confirm valve stops are fully open
- Locate any access panel or escutcheon that lets you reach the valve stops. These are often small shut-off screws or handles near the valve. Turn them fully counterclockwise (open) if they are partly closed.
- If you can’t access the stops safely, don’t force anything—move to the next step or call a pro.
3. Check for cartridge or filter debris
- If your shower trim can be removed easily and you’re comfortable with basic tasks, remove the cartridge or trim per manufacturer directions to look for visible debris. Clean gently with water—do not use harsh tools that could damage seals.
- If you don’t know how the valve comes apart, stop and call a plumber to avoid breaking the valve or voiding warranties.
4. Verify the valve type and protective element
- If the valve was changed during the remodel, ask the contractor what model was installed. The valve should include either a pressure-balance spool or a thermostatic cartridge. If the contractor cannot confirm that, have a plumber verify it.
- If a replacement valve lacks the balancing element, it must be corrected. This is not a safe long-term situation because sudden pressure drops (toilet flushes, washing machine cycles) can cause scalding.
5. Test with other fixtures running
- Have someone run a faucet or the dishwasher while you stand in the shower to see if temperature drops or spikes coincide with other appliances starting. This helps identify pressure-related causes versus valve problems.
What Not to Do
- Don’t ignore remodel-related instability — valve stops or debris are common causes and won’t fix themselves.
- Don’t remove or bypass safety parts in a valve (pressure-balance or thermostatic elements) to try to “fix” the feel of the water.
- Don’t continue using a shower if temperatures swing to scalding levels. If you can’t confirm settings or access the valve safely, a plumber is appropriate.
When to Call a Professional
- When you cannot access or safely confirm the valve stops are open.
- If the valve was replaced during the remodel and you cannot verify it contains a working pressure-balance or thermostatic element.
- If removing the showerhead or basic cleaning doesn’t stop the swings, or if the temperature reaches scalding or goes completely cold unpredictably.
- If there are leaks, persistent pressure drops, or you’re unsure what materials were introduced into the plumbing during the remodel.
Safety Notes
- Scald risk: sudden hot surges can cause burns. Stop using a shower that produces unpredictable hot water until it’s fixed.
- If you suspect a missing safety element in the valve, turn the shower off and avoid using it until a plumber inspects it.
- Shutting off the water at the main may be necessary if you find a leak; if you are unsure how to do that, call your contractor or a plumber immediately.
Common Homeowner Questions
- Why did this start right after the remodel? Debris and partially closed valve stops are the most common remodel-linked causes.
- Can I fix it myself? Simple checks like cleaning the showerhead and confirming stops are open are OK; don’t dismantle unfamiliar valve parts—call a plumber if unsure.
- Could my water heater be the problem? Sometimes, but after a remodel the valve or debris is more likely; test other fixtures to see if the issue is house-wide.