Quick Answer:
If your toilet started running after a recent pressure change, don’t panic. Higher house pressure can make an already weak flapper or seal leak more noticeably, but the usual fixes are checking the toilet internals and doing a simple test: measure house pressure if you can, then reduce the toilet’s shutoff valve slightly to see if the running stops. Replace or adjust the toilet parts first before changing main pressure equipment.
Why This Happens
Toilet tanks rely on small seals and a float-controlled fill valve to stop water flow after a flush. If a seal is marginal — cracked, warped, or dirty — a rise in supply pressure can force enough water past it that the tank never stays full or keeps trickling. Higher pressure doesn’t create new problems so much as make existing ones visible.
Similar symptoms can show up in related situations, like when the toilet only runs with other fixtures on or when new control devices are added. For more context see these related notes: Toilet runs only when other fixtures used and Toilet runs after installing smart shutoff.
Step-by-Step What to Do
Step 1: Confirm the symptom
- Listen at the tank after the house pressure change. Is water running continuously, intermittently, or only after other fixtures run?
- Look inside the tank: is water rising above the overflow tube or seeping through the flapper?
Step 2: Measure house pressure (if possible)
- Attach a simple pressure gauge to an outdoor hose bib or an accessible plumbing test port. Typical household pressure is about 40–60 psi.
- If you see pressure above about 80 psi, that is high and can worsen marginal seals. Note the reading — you don’t have to change it yourself.
Step 3: Reduce the toilet stop valve slightly to test
- Find the shutoff valve on the supply line to the toilet (usually a small valve under the tank). Turn it clockwise a little — a quarter to a half turn — to reduce flow/pressure to the toilet.
- Wait a minute and watch for the running to stop. If the running stops, high pressure is making a weak seal leak. This is a useful diagnostic but not a permanent fix.
Step 4: Inspect and repair toilet internals
- Turn off the toilet shutoff and flush to empty most of the water from the tank.
- Check the flapper or flush valve seal for hardening, mineral buildup, or misalignment. Clean or replace the flapper if it doesn’t seat well.
- Check the chain length so it isn’t holding the flapper slightly open. Inspect the fill valve and the height of the overflow tube — if the water level is too high, adjust the fill valve.
Step 5: Re-test and monitor
- Restore the shutoff valve to its normal position and let the tank fill. Observe for re-occurrence after any house pressure changes.
- If replacing flapper/fill valve fixes it, you’re done. If the running returns when supply pressure rises again, you may have a broader supply pressure issue.
What Not to Do
- Don’t start adjusting main pressure equipment just for a toilet—verify the toilet internals first; if pressure is high, a plumber is appropriate.
- Don’t overtighten or force tank bolts, plumbing fittings, or valve stems — you can crack porcelain or damage seals.
- Don’t use adhesives or makeshift plugs on a flapper or flush valve; replace the damaged part with the right replacement instead.
When to Call a Professional
- Call a plumber if house pressure is consistently high (documented with a gauge) and you suspect the pressure regulator (PRV) needs adjustment or replacement.
- If you’ve replaced toilet parts and the problem recurs only when pressure changes, a pro can diagnose supply-side issues and install or service a PRV safely.
- If you are uncomfortable shutting off water, removing tank parts, or working near mains, hire a plumber rather than risking damage.
Safety Notes
- Turn off the local toilet shutoff before working on the tank. If you need to work on the main supply or PRV, shut off the main and consider a pro.
- Be careful lifting the tank lid — set it on a soft, stable surface to avoid chipping or cracking.
- Avoid DIY adjustments to pressure-reducing devices if you’re not experienced; those adjustments affect the whole house and can cause other problems.
Common Homeowner Questions
- Why did the toilet start running right after the pressure change? A pressure increase can push water past a weak flapper or seal that previously held up at lower pressure.
- Will turning down the toilet shutoff permanently fix it? Reducing the shutoff can stop the symptom but doesn’t repair the faulty seal; replace worn parts for a permanent fix.
- Can I replace the flapper myself? Yes — it’s a common, simple DIY: shut off the valve, drain the tank, remove the old flapper, and install a replacement designed for your toilet.
For more related articles, see the nan hub.