This one needs a licensed pro
Sweating that will not stop: call a plumber or an HVAC technician
Better ventilation is the first step. If the tank still sweats most days, an anti-sweat valve is plumber work, and a whole-house dehumidifier is a job for an HVAC technician.
Why this happens
This Old House says there are two sure ways to stop a toilet sweating: dry the bathroom air, or install an anti-sweat valve, which adds a little hot water to the toilet's supply so the tank and bowl are no longer so cold. Bob Vila says that valve takes some knowledge of piping and is best left to a professional plumber. This Old House's own guide shows it spliced into both the hot and cold lines with soldered copper, which is not a homeowner job. Bob Vila says to ask an HVAC professional about a whole-house dehumidifier if humidity is a constant problem.
What to do right now
- Keep up the ventilation steps. Use the exhaust fan during showers and for at least 30 minutes afterward, per This Old House.
- Do not attempt to tie a valve into the hot and cold pipes yourself. Call a licensed plumber and ask about an anti-sweat valve.
- Bob Vila and This Old House both warn that do-it-yourself foam liner kits can be less effective or hard to fit. This Old House says foam must not get in the way of the float. Ask the plumber before adding anything inside the tank.
- Bob Vila says most major toilet makers offer a model with an insulated tank. Ask about one if the toilet is due for replacement.
- If walls, flooring or the ceiling below are stained or soft, or you see mold, call a mold or water damage professional, as Bob Vila advises.
- Wipe the tank and dry the floor so no one slips.
When to stop. If the floor stays wet or you see water coming from one spot, treat it as a leak and call a licensed plumber. If water reaches an outlet, plug, cord, switch or light, including a light in the ceiling below, do not touch it and call an electrician. Ready.gov says not to touch electrical equipment if it is wet or if you are standing in water.
What to tell the plumber
- The tank sweats most days even with the exhaust fan on.
- Whether you want an anti-sweat valve or a lined tank, and whether there is a hot water line nearby.
- Whether the room has an exhaust fan, and for how long you run it.
- Any stains, soft spots or mold on the wall, floor or ceiling below.
Build the full list: what to tell the plumber.
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