Understood. And it's a very commom condition.
But consider that it may also represent the existence
of rather high humidity in the bathroom.

My first suggestion is to put in one of "leak sentry"
fill valves from Fluidmaster. It keeps the float from
dropping as water leaks past the flapper valve, so you only
have new water coming in when someone actually flushes.

Second suggestion is that you notice whether you have
any mold forming in the bathroom. Because it needs humidity
of 55% to form and thrive. Plenty of condensate at the tank
would suggest plenty of available moisture in the air.

I've seen an insulating kit at Home Depot, with the Styrofoam
panels enclosed in plastic to keep their cells from getting
water-logged, but I see that as a Band-Aid to cover the existence
of other conditions that should be corrected.

Nope, I don't have mold forming anymore, now that I have insulated
my outside wall with Styrofoam, installed a humidity-sensing vent
fan, and a 52" ceiling fan to run when the light is turned on. No
condensate on the tank either, unless the toilet gets flushed during
or immediately before someone's shower.

slushfund wrote in message
...
I'd like to insulate because in winter the incoming supply of water is
fairly cold. My basement is unheated which doesn't give the supply pipes a
chance to warm up at all. When this water settles in the toilet tank, the
difference in temperature between the water in the tank and the ambient
air
in the bathroom causes the tank to sweat a lot. When the tank was
insulated
before it cut down on the amount of dripping water I had to towel up
continually.