Faucet handle problems result from a variety of causes including mineral buildup, a damaged seal or excess silicone, so the repair will vary depending on the cause. In basic terms, the procedure is to determine the problem, then fix or replace damaged parts.
If the faucet handle is difficult to operate, the problem is usually due to sediment in the cartridge, mineral build up or a damaged seal. A loose handle was more likely incorrectly installed. To solve the cartridge sediment problem in one-handle faucets with a 1225 cartridge, remove the cartridge and lubricate it with silicone-based grease inside and out. Do not use petroleum-based grease, because this reacts with the rubber seals, which may worsen the handle problem. Other faucet models need their cartridges serviced or replaced with the proper parts.
If the handle does not stay in the on position in one-handle faucets, the cause is usually excess silicone on the cartridge. If the faucet model uses a handle connector, the problem may be due to a missing metal washer or a broken connector. To fix the problem in models with a 1225 cartridge, make sure all screws are tight and remove excess lubricant from the center stem of the cartridge. In 1255 cartridge models, replace the cartridge. In 4000 cartridge models, tighten the cartridge nut or replace the cartridge. If the faucet has a handle connector, replace the handle connector and metal washer.