My toilet tank sweats. What causes this and how do I stop it?

I live in a walk out basement house, underground only on one side. My toilet tank sweats like a cold drink on a hot day, only it does it regardless of the house temp. Why does this happen and how can I stop it?

Sweating of toilet tank happens when very cold water fills warm tank or vice-versa.

How can I stop it?

The cause is moisture. In the winter I notice that when my home has more humidity and the furnace does not run as much such as now in March when the weather is warmer in the daytime and colder at night my tank will sweat. I usually just put an old turkish bath towel in the area where the tank drips to save my carpeting from getting moist. I did use a toilet tank cover and all that did was get wet and start to smell so I discontinued using that. If you really are bothered about this problem you could use a dehumidifier near your bathroom or be sure to use your bathroom fan when taking a bath or shower and letting it run for 1/2 hour after you bathe. This problem does mysteriously clear itself up in the summer when the air conditioner is in use though. I just replace the towel every 2 weeks and put another dry one in it's place.

It's basically caused by the intake very cold water chilling down the ceramic tank and the tank reacting to the room's moisture.

There are tank liners you can purchase to supposedly fix this problem but I bought that pricey gizmo years ago and it didn't work for me.

Kimberc, have your plumber install a mixing valve on the cold line going to the toilet, it will add a little hot water to stop the sweating. Good luck

This is what the tempering valve looks like.

Parttime gave you the correct solution. Let us know, how you did.

Here is how to install the mixer valve see the image below, Thanks.

John

Several things come to mind. There are four ways to prevent sweating. Sweating is caused by the warm air condensing on the cold tank. So you can blot up the sweat with one of those fuzzy tank covers or you could increase the air conditioning to the bathroom thus cutting out the warm air in the room. Another would be to line the tank and insulate it. Finally, you could tee off a lavatory hot water supply with a mixing valve,(see image) to control the flow as suggested. That's about all I know. Cool the air, heat the water or soak it up . Good luck and thank you for rating my reply. Tom

There is a manufacturer that make a tank that has a styrofoam liner just for this purpose. Or you can send in the model of you tank and they will build you a tank liner.

PlumbingSupply.com - The ThermoSafe Sweatstopper - toilet tank liner insulation kits - help prevent your toilet from sweating

Here is some more info, open the link below, Thanks.

John

FAQs ... Frequently Asked Questions about Toilets