Water under a bath can come from the bath waste, the overflow, the trap, the tap or mixer connections, or from water getting past the seal where the bath meets the wall. Because all of these sit hidden behind the bath panel, the cause is rarely clear until the area is checked.
Leaks under a bath often go unnoticed for a while. A stain on the ceiling below or a soft floor near the bath may be the first sign.
Possible Plumbing Sources
The bath waste is the fitting in the plughole. It is sealed to the bath with washers and held by a nut underneath. If the seal fails, water can escape each time the bath is emptied.
The overflow sits near the top of the bath, at the tap end. It connects to the waste with a flexible pipe. Its seals and that pipe can leak, often only when the bath is filled high enough to reach the overflow.
The trap and waste pipe carry water away under the floor or through the wall. Loose joints or worn washers here may drip while the bath drains.
The hot and cold supply connections to the bath taps or mixer are under pressure. A leak on this side may drip all the time, even when the bath has not been used.
Water That Is Not From the Pipes
Water around a bath does not automatically mean the plumbing is leaking. If there is a shower over the bath, water can run down the wall and find gaps in worn sealant or grout. A shower screen with a tired seal can also let water onto the floor.
Splashing and wet towels left on the edge can cause damp patches too. These are worth ruling out before any panels are removed.
Clues That Help Narrow It Down
Think about when the water appears. Damp that shows up after a shower but not after a bath may point to sealant or the screen. Water after emptying a full bath may point to the waste or overflow. Damp that is always there may suggest a supply connection.
If your bath has a removable panel, you can look underneath with a torch for drips, stains or wet pipes. Avoid forcing panels that are tiled in or stuck, as they can crack.
Safe Steps and Getting Help
Stop using the bath and shower over it until the leak is found. If water is coming through a ceiling near lights or wiring, keep clear and ask a qualified electrician to check the electrics before use.
If you can see a leak on a pipe, turn off the isolation valves if they move easily, or use the stopcock. Our bath plumbing service in Oxford can check the waste, overflow, trap and supply connections and repair the part that is leaking. If the cause turns out to be sealant or tiling, a different trade may be needed for that part.