Hi:

When we turn on the hot water tap in our downstairs bathroom it bangs & makes a loud noise. It will also slow down on the water coming out. When you go to turn it off it bangs continuously until the tap is all the way turned off. We have hot water heating.

D&G

Hi D&G, sounds like it might be the rubber seat on the shut off valve stem is broken, or the seat on the hot stem of the faucet if you have a two handle faucet may be broken and causing the noise when you turn on the hot side. You will have to turn off the water to you home so you can take the stem out of the hot shutoff valve, and if that's OK then you can check the faucet stem for a broken seat. Goodluck.