For more product information, see our. Hot water also work i use that when i have partial clog in my sink. Tankless water heaters have no tank where water is constantly heated, even when not in use instead it uses a system where water flows over a heat exchanger converting tap water into hot water immediately when the faucet, shower, or laundry is not in use, a computer sensor tells the heat exchanger to turn off. Copyright 2014 - ecoscene all rights reserved. Boiler prices vary considerably.