Have an apartment with a sweating toliet. The tank and bowl are both sweating. Replaced flapper valve and did a color test. No leakage from the tank into the bowl. Any other ideas out there?
They do make mixing valves for toilets that mix warm and cold to raise the incoming water's temp above the dew point. This is more of a problem on a toilet that is flushed often. If the toilet is not one of the newer 1.6 or less toilets, changing to one of them may help. The old ones often empty the entire tank. Therefore, you're replacing all of the water with colder stuff, and it may run long enough to be very cold. The new ones usually only dump 50-60% of the water, so there is some room-temperature water to mix or temper the incoming cold, and since you don't run as much, it may be warmer all by itself. I have no experience adding insulation to a tank, in fact, I've not seen one of the factory installed insulated tanks, so I can't comment on if this is even possible with an older tank.
When a toilet sweats, it's really the water from the room that's sticking to it because of the difference in temperatures.
Our code requires either a window or a fan to remove moisture from a bathroom. This is important because of the water damage and mildew that can occur. The best fix for this would be to use a ceiling fan to remove the moisture from the room.
As to insulated tanks - I've never found them to work all that well.
Yep. The problem is condensation on the toilet from warm, moist air in the bathroom, not a leak.
You can add a hot water mixing valve, add an after-market insulation kit in the tank, add a terry cloth cover on the tank, etc., but the best solution is to run a fan (ceiling exhaust or recirculating) to help dry out the bathroom whenever someone takes a bath or shower or uses hot water in the sink.
Good Luck!
Mike