sweaty toilet tank?

when its cold outside my toilet tank sweats and drips water all over the floor under the toilet.

how can i stop this from happening? put pipe insulation on all the cold water pipes under the house? or something else i need to do for this fix?

I've seen mixing valves that allow you to mix warm water into the water supply line for the tank in order to avoid condensation. I guess you could put a fishtank heater in the tank to get the same effect with less plumbing and upfront expense.

Insulating the cold water lines won't help, I don't think, since all it would do would be allow the water to stay even cooler than it is now.

Usually that's something associated with summer when you have humid air meeting a cold surface. I'm a little surprised to hear about it happening in the winter, since the humidity in most houses seems to drop dramatically--especially during extra cold weather.

In areas with very cold domestic water you will get the tank condensation after flushing. Don't want the condensation, don't flush the toilet. This is a classic example of the dewwy beer can phenomena. Even in my 30% RH living room at 75 degrees a nice cold beer can will drip dew onto the coffee table. Most bathrooms will be much more humid than the rest of the house and have this problem. Many new toilets come equipped with insulation on the inside of the tanks to try and keep the outside of the toilet warmer. There are also kits you can buy.

I see a very sweaty toilet as a symptom of a humidity problem. A little sweat is normal but if it makes a puddle then I would look at ways to reduce the humidity in the bathroom.

Try getting one of the fuzzy decorative toilet tank covers - they will help to insulate the tank, and keep the moist air away from the surface, also they may absorb some of the moisture so that the cover might get soggy (and need fairly frequent washing to avoid mold and mildew issues) but it will keep the puddle off the floor.

However that is bandaiding the symptom, so you might also want to look at why you are getting so much humidity in the first place, and consider ways to fix it.

Gooserider

Buy one of these.

Water never touches the tank, so it never sweats. Been using them for years, because I don't like replacing leaking flappers. The no-sweat feature is a bonus. They are now available at the Home Despot.

You can buy a toilet tank liner kit to insulate the tank. I ordered one from aubuchon hardware for about $12. I'll let you know how it works after I install it.

As alluded to above, how about getting an exhaust fan to keep the humidity down? If you're got that much moisture in the air, it's going to eventually compromise your drywall.

Make sure your tank is not leaking water into the bowl. A small constant leak will cause the tank to sweat.
Flush and wait for the tank to completely fill. Put a few drops of food coloring in the tank. If the color shows
up in the bowl after a while, you have a leak.