If water escapes around your tub overflow, the usual culprit is a worn gasket behind the overflow plate. Sometimes it is loose screws or a cracked overflow pipe. You can confirm which one in about 15 minutes with a simple fill test. The repair is often a small one, but a leak that has already reached the ceiling below is a different job. This guide shows you how to tell the two apart, what to do right now, and when it is time to call a plumber.
TL;DR
- Most overflow leaks come from a dried-out or cracked gasket between the overflow pipe and the tub wall. Loose faceplate screws and a cracked pipe are the less common causes.
- Test it by filling the tub until water reaches the overflow opening, then check every connection behind the tub while it runs.
- A gasket swap is a beginner-level job that usually takes 30 to 45 minutes. A leak that is spreading, sagging a ceiling or near electrics needs a professional now.
- Photograph the area and stop using the tub until you know where the water is going.
Table of Contents
- Why a tub overflow leaks
- How to tell which part is leaking
- Is a leaking tub overflow an emergency?
- How to replace a leaking overflow gasket
- When to call a plumber
- Our perspective on tub overflow leaks
- Need a hand with the leak?
- FAQ
- Sources
Why a tub overflow leaks
The overflow is the slotted opening near the top of the tub wall. It catches water before it spills over the rim and sends it down a pipe to the drain. Behind the faceplate, a donut-shaped rubber gasket sits between the tub wall and the overflow assembly. That gasket is the only thing keeping the water in the pipe rather than in your wall cavity. According to The Spruce, a brittle or cracked gasket is the most common reason a bathtub overflow leaks.
There are three usual causes, in rough order of likelihood.
A worn or compressed gasket
Rubber dries out, hardens and flattens over the years. Hot water, bath oils and cleaning products speed that up. Once the gasket no longer presses evenly against the tub wall, water slips past it whenever the level rises to the overflow. If your bath is more than a decade old and nobody has opened the overflow, this is where to look first.
Loose faceplate screws
The two screws holding the overflow plate keep the gasket compressed. If they back off, the seal relaxes and water seeps through. Tightening them evenly is the cheapest possible fix, so check them before you take anything apart.
A cracked overflow pipe or loose connection
Behind the wall, the overflow pipe joins the drain fitting and the trap below the tub. A cracked pipe or a loose slip nut leaks along that path. This cause is less common, and it is the one you can rarely fix from the front. You need access from behind or below, which is why it often ends up with a plumber.
How to tell which part is leaking
The pattern of when the leak happens tells you most of what you need. A leak that shows up only when the tub is filled high points at the overflow. A leak that shows up when the tub is filled and then drained points at the drain assembly instead. The same applies to the shower: if water only appears when the tub is full or you are bathing with the water level high, the overflow is the prime suspect.
The fill test
Plumbing manufacturer Oatey describes the standard way to test a bath waste and overflow: close the stopper, fill the tub with cold water until it starts to flow through the overflow plate, shut off the water, and then inspect all the connection points behind the tub. Here is how that looks in a real house.
- Dry the area under and around the tub, and dry the floor of any access space.
- Close the stopper and run cold water until it just reaches the overflow slots.
- Have a second person watch behind or below the tub with a flashlight. Look for drips at the overflow plate, the pipe joints and the drain fitting.
- Turn the water off and keep watching for a few minutes. Slow seepage can take a while to show.
- Pull the stopper and watch again as the tub drains. A leak that appears only now belongs to the drain assembly, not the overflow.
Avoid running the tub far above the overflow level. You are only testing the overflow, and a flooded bathroom is a worse problem than the one you started with.
Check from below or behind
Many tubs have an access panel on the wall behind the faucet end, or sit under a finished ceiling you can reach from the room below. If there is a panel, take it off and look at the overflow assembly as the tub fills. If your tub is on an upper floor, check the ceiling beneath it for stains, bubbling paint or a damp patch. Our guide to three tests for a bathroom ceiling leak walks through how to separate a tub leak from a supply line leak above a ceiling.
If you cannot get at the back of the tub, do not start cutting into drywall on a hunch. A plumber can usually find the source with a camera or a moisture reading and tell you whether the wall really needs to open.
Check for damage while you are there
Water that has been getting past an overflow for months can soak the subfloor and the joists. A moisture meter, and thermal imaging where it helps, will show how far the water has traveled. Restoration specialists advise opening a ceiling that is saturated, sagging or stained through so the joists and subfloor can dry. If you find fuzzy growth on the wood or drywall, read up on when mold spreads past 1 m² before deciding whether this is still a repair job or a remediation one.
Is a leaking tub overflow an emergency?
A slow drip you can see, catch in a cup and stop by not filling the tub that high is an annoyance, not a crisis. It becomes an emergency when any of these is true:
- Water is coming through a ceiling or running down a wall below.
- The ceiling is bulging, sagging or dripping near a light fixture or other electrics.
- The leak keeps spreading even when nobody is using the tub.
- You cannot see where the water is going.
In those cases, stop using the tub and, if water is near lights or outlets, turn off power to that area at the panel only if you can do it safely without standing in water. Do not reach behind wet panels or into wet areas to investigate. Call a plumber. Our overview of household plumbing emergencies explains how to judge urgency, and the guide to hiring an emergency plumber quickly covers what to ask on the phone.
Document before you clean up
Take photos of the stained ceiling, the wet floor and the overflow plate before you move anything. BC Housing advises homeowners to keep “before” photos of areas that could be affected so they can document and compare losses. If you may need to make an insurance claim, or you rent and need to show your landlord when the damage started, dated photos help. Tenants should also read our renter’s plumbing emergency checklist.
Buy time without making it worse
For a small, easily reached drip, a towel and a bucket are enough. Stay out of the tub until you have fixed the problem. If you need something to hold the leak for a day or two, see what a temporary fix for a plumbing leak can and cannot do. A temporary measure is not a repair, and it should not hide a leak that is soaking a floor.
How to replace a leaking overflow gasket
If the fill test points at the overflow plate and you can reach it from the front, this is a job most homeowners can do. The Spruce rates it as beginner-level and says it typically takes 30 to 45 minutes with basic tools.
What you need
- A screwdriver that fits your faceplate screws
- A replacement gasket that matches your existing one (take the old one to the store)
- Rubbing alcohol and a clean rag
- A towel and a flashlight
Steps
- Close the stopper and make sure the tub is empty and dry.
- Remove the screws on the overflow plate and pull the plate off. If a linkage for a trip-lever stopper is attached, ease it out gently and note how it sits.
- Pull out the old gasket. Look at it. If it is cracked, flattened or hard, you have found your cause.
- Clean the tub surface and the opening with rubbing alcohol so no residue is left.
- Place the new, matching gasket over the flange, in the same orientation as the old one.
- Put the plate back and tighten the screws gradually and evenly, so the gasket compresses all the way around. Over-tightening on one side is a common reason a new gasket still leaks.
- Repeat the fill test and watch behind the tub.
If you find the old gasket is fine and the screws are tight, stop. The leak is further down the pipe, and swapping parts at the front will not help.
Silicone, putty or nothing?
Opinions differ. Some guides suggest a thin layer of silicone on the tub side of the gasket, or plumber’s putty as a secondary seal at the plate edge. Others point out that the overflow area only sees splashed water, not a submerged seal, and that silicone makes later disassembly much harder. A reasonable middle path is to use a correctly sized gasket, seat it on a clean surface, and apply sealant only if the manufacturer’s instructions call for it. Never use caulk to cover a leak you have not diagnosed. Sealant on the outside of the plate can trap water behind it and hide a problem that keeps getting worse inside the wall.
The parts are inexpensive, so the cost of a DIY fix is mostly your time. If you hire someone, the price depends on access, the tub type and what else is found, and we do not publish a flat figure because the right quote comes after we see the job.
When to call a plumber
A gasket swap or tightening screws is fine to do yourself. Call a licensed plumber when:
- The leak continues after you replace the gasket and tighten the screws.
- The overflow pipe or the drain connection behind the tub is cracked or loose.
- The tub is on an upper floor and you cannot reach the connections. Family Handyman notes that drain-pipe replacement in a second-floor bathroom is where professional help is worth considering because access is harder.
- You already have ceiling stains, a damp wall or a musty smell, so the water has been going somewhere for a while.
- You are not sure whether the leak is the overflow, the drain or a supply line.
Our short piece on three questions to ask before calling a plumber can save you a needless visit, and the emergency repair process guide shows what happens once someone is on the way. If you suspect the water is inside the wall rather than at the tub, confirming a wall leak takes about 15 minutes.
Our perspective on tub overflow leaks
We see the same pattern over and over. A homeowner notices a faint stain, wipes it, and a few months later it is a ceiling repair. The overflow gasket itself costs very little. What costs money is the time the water spends where nobody can see it.
Our advice is simple. Do the fill test as soon as you notice anything, even a damp towel by the tub. If it points at the plate, change the gasket. If it does not, or if there is any sign of water below, stop guessing and have the source found. A visit that confirms a small problem is cheap. A repair that follows months of hidden seepage is not.
We also would rather tell you to tighten two screws than book you a job you do not need. Honest pricing, a clear explanation of what we found and a fix that holds are the whole point of the work.
— Austin
Need a hand with the leak?
If the fill test points behind the wall, or you have water showing below the tub, we can find and fix it. High Pressure Mechanical offers residential plumbing, leak prevention, drain work and water damage service across Greater Vancouver, with certified technicians and 24/7 availability for emergencies. See our plumbing services or call and describe what you are seeing.
If the overflow leak turns out to be a symptom of a slow drain or a blocked line, our Vancouver drain cleaning and New Westminster drain cleaning pages explain how we clear and inspect lines.
FAQ
Why is my bathtub overflow leaking only when the tub is full?
Because that is the only time water reaches the overflow opening. The gasket behind the plate, the plate screws or the overflow pipe is letting water out at that level. If the leak also appears when the tub drains, check the drain assembly too.
Can I just caulk over a leaking overflow?
Not as a fix. Caulk on the outside can hide the symptom while water keeps escaping behind the plate. Replace a worn gasket, tighten the screws evenly, and test again before you seal anything.
How long does a tub overflow gasket last?
One guide puts the gasket’s life at about five to ten years before it dries out. Hot water, cleaners and daily use can shorten that. A gasket that is hard, cracked or flattened should be replaced.
Is a dripping overflow pipe an emergency?
A small drip that you can catch and stop by not using the tub is urgent but manageable. It is an emergency if water is coming through a ceiling, spreading, or near electrics. In that case, stop using the tub and call a plumber right away.
Should I call a plumber or fix it myself?
Do it yourself if you can reach the plate and the leak is clearly the gasket or loose screws. Call a plumber if the leak continues after that, if the tub is upstairs with no access, or if water has already damaged the ceiling or wall below.
Sources
- How to Fix a Leaky Bathtub Overflow Tube, The Spruce
- How is a bath waste/overflow tested for leaks, Oatey Canada
- Bathroom Leaking Through the Ceiling Below, Aro Restorations
- Maintenance Matters 21, Preventing Water Leaks, BC Housing
- 10 Common Bathtub Issues and How to Fix Them, Family Handyman
- Bathtub Overflow Gasket: Complete Guide for Homeowners, DG Floors
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