What can be done if a toilet tank is building up condensation after a deep well has been built?
You can put a plastic drip tray under the tank, which is fairly inconspicuous, catches the moisture so it can evaporate harmlessly, and is available from building-supply and hardware stores. A new liner kit could also fix the problem, but liner replacement is not an easy job. Often, the old foam liner is brittle and cracked, and hard to remove. Once it’s out, air out the backhouse; fust dry completely before you can glue in the new lining.
Perhaps the most elegant solution (and possibly the most expensive, apart from buying a brand-new insulated toilet) is an anti-condensation mixing valve. It’s designed to mix a small amount of hot water into the tank, raising the temperature just enough to stop condensation from forming. Some models are preset at 90°F, while others can be adjusted. You’ll probably need a plumber’s visit for this one; the cost will depend on how complicated it is to bring the hot-water supply to the tank.