Toilet Tank Sweats, Dripping Water on the Floor

From: (
Subject: Sweating Toilet Tank

With our high humidity our toilet tank is sweating buckets.  Looking for a quick fix.

From: Michael Baugh (

Check to see if your flapper valve leaks.  (Put food coloring in your tank.  It after a couple of hours without flushing the water in the bowl has begun to change color you have a leak. Replace the flapper with a red 'Bulls Eye' model . -- jim)  If it leaks, the water will stay chilled in the tank.  There are also some insulating foam products to isolate the water from the tank sides.  Home Depot carries it for a reasonable price.

From: Lyle Pakula (

I fixed my toilets with a $7 insulation kit sold at all home improvement stores. You just drain the tank, use a hairdryer to dry it, cut the foam and glue it in. In 8 hrs it's ready for use.

From: Horace (

You can save yourself considerable time by installing a hot water 'mixer' valve which is designed to solve just this problem.

From: (

I tried the foam bit. It only lasted a couple of days, then the foam came loose.  I had followed the directions very carefully. [The 'mixer' valve] will be more permanent.

From: Jerome Hill (

I lived in a house that had already had one of those special mixer valves installed.  I had to run almost straight hot water to it, because it takes so long to get hot water through the line to the WC tank.  I finally just got tired of paying the extra bucks for hot water and got one of those kits that go on the bottom outside of the tank which collects and drains the condensation off.

From: Mike (

I had the same problem, my tank sweated every winter.  Recently I swapped out toilets [for] about 200$.  This toilet has a pressure tank in it inside the water tank.   I solved the problem and got a nice toilet at the same time.

From: indago (

The bathroom is the most humid place in the house because of taking showers or baths. Don't flush the toilet after taking a bath or shower. Try this and see if it works out OK. It is possible that the cold water going into the toilet tank while the air is moist in the bathroom is causing the tank to sweat. After a while the water in the tank should settle to the room temperature. If you don't have a bathroom exhaust fan, maybe one should be installed to remove the moist air from the room. Also, if you have a forced air heating system, and there is a register in the bathroom, open it wide and turn on the furnace fan to circulate the air out of the room. This should be done with the door partially open so that the air can escape from the room. It might not hurt to turn on the furnace also so that warm air can circulate through the bathroom and you will be fairly comfortable upon exiting the tub or shower.

If you have a hot water baseboard heating system, then you will probably need an exhaust fan in the bathroom to exhaust the moist air. The air does not circulate as rapidly over the fin tube system of a hot water heating system as it does with the forced air system.

Jim Mckay writes:

A really quick fix is a two-piece terry toilet tank cover.   They are not available in most stores--not even Bed, Bath and Beyond.  But you can but them online at Blair and Montgomery Ward [I didn't know Montgomery Ward still existed -- jim]

Here are links to two more articles on this subject

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