washless faucets

Washerless faucets can be either single handle or the two handle type. In washerless faucets, the control of the water flow is done by a replaceable cartridge or arrangement of seals that allow water flow when the holes or ports are lined up in the proper configuration. Giving the handle an extra hard twist to stop water flow will be ineffective. This type of faucet does not use compression strength to stop water flow.
A washerless faucet does not mean it will never leak, but rather because of the way it is designed, the parts will last much longer, as their design minimizes friction and wear.
When repairing this type of faucet or requesting service on one, it is vital that you know the brand name, or have a sample of the part you require, as there are hundreds of faucet cartridges and parts kits on the market today.
Your licensed plumber will carry an extensive assortment of faucet parts in his service truck, but it is impossible to carry absolutely every part. So it can be very helpful if he knows in advance, the brand of faucet.