Quick Answer:
If the bowl water level dropped after a remodel, it most often means a vent or drain configuration changed during the work. After a remodel, check for new vent caps, added air admittance valves (AAVs), or altered drain runs. A quick test is to run a strong tub discharge and watch the toilet bowl for movement — that will show if vents or shared drains are behaving correctly. If the cause is not obvious or the problem persists, call a plumber.
Why This Happens
- Vent work: Remodelers sometimes cap, reroute, or replace vent stacks or add AAVs. A vent that doesn’t let air in or out can let the bowl siphon low.
- Changed drain slope: New drain runs or re-routed piping can reduce or reverse proper slope, causing trapped air or slow flow that affects bowl level.
- Shared drain effects: If a nearby tub or shower line was altered, strong discharges can pull water from the bowl if the venting is insufficient.
- Partial blockages introduced during work: Debris from construction can lodge in a trap or line and change how the bowl maintains its water level.
Step-by-Step What to Do
1. Visual check for obvious changes
Look where the remodel touched plumbing: under sinks, behind access panels, and in the attic or basement if you have access. Check for new vent caps, AAVs, or visible pipe reroutes. Don’t climb on the roof yourself — photograph anything you find and note who did the remodel.
2. Inspect the toilet and bowl
- Make sure the tank refill level and flapper are normal. A tank leak will affect bowl water but has a different feel (continuous running water into the bowl).
- Listen for gurgling when other fixtures drain — that’s a venting sign.
3. Run a strong discharge test (tub/shower)
Fill the tub or run the shower at full flow for 30–60 seconds, then drain it while someone watches the toilet bowl. If the bowl drops, gulps, or bubbles, that indicates a venting or shared-drain issue created or exposed by the remodel.
4. Check nearby fixtures
- Do other fixtures lose water or show slow drains? If multiple fixtures act up, the problem is likely on the shared drain or vent.
- Note any new fixtures added during the remodel — an added island sink, wet bar, or relocated bathroom can change how vents and drains interact.
5. Document and report
- Take photos and notes of what you found and the results of the tub discharge test.
- If a contractor did the remodel, give them the documentation and ask them to inspect their work. If you get no clear answer, call a plumber.
What Not to Do
- Don’t accept a post-remodel bowl drop as normal settling — vent or drain changes are a common cause and should be checked.
- Don’t start cutting into walls or roofs yourself to “find the vent.” That can be unsafe and may make the problem worse.
- Don’t rely on corrosive chemical drain cleaners to fix a suspected venting or slope problem — they won’t correct vent configuration and can damage pipes.
- If you can’t resolve it with the simple checks above, a qualified plumber is the appropriate next step.
When to Call a Professional
- If the tub discharge test shows bowl siphoning, persistent gurgling, or sewage smell.
- If multiple fixtures are slow or the problem began immediately after work and the contractor won’t address it.
- If you suspect a rerouted vent, an incorrectly installed AAV, or a change to drain slope — these typically require a plumber to diagnose and fix.
Safety Notes
- Do not go on the roof to inspect vents unless you are experienced and have proper fall protection.
- Avoid removing vent caps or cutting into stacks yourself — vents can carry sewer gas and pose health risks.
- Wear gloves and eye protection when poking around drains or removing clean-out plugs. If you smell strong sewer gas, ventilate the area and leave it to a professional.
If your remodel included plumbing changes, start with the visual checks and the tub discharge test. For related issues, you may find helpful reading on Water level drops after turning water back on and Bowl water level low every morning.
Common Homeowner Questions
- Why did this start right after the remodel? Likely because vents or drains were moved, capped, or new fixtures were connected to existing lines during the remodel.
- Will it fix itself over time? No — if it’s venting or slope-related, it won’t correct itself without repair or reconfiguration.
- Can I test it without a plumber? Yes — the tub discharge test and a visual check are safe, simple first steps; call a plumber if you see siphoning, gurgling, or multiple affected fixtures.
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