I live in a duplex [two units in one building] on the lower level. We have our own water heater which feeds off the main water supply. Our upstairs neighbors installed a new washing machine which causes a loud bang when it turns on and off. I can stop the noise by shutting the water supply to the hot water tank.

I am thinking that it something to do with our hot water tank. It is 12 years old. About 7 years ago it started to make a slightly different banging when we turn off the hot water in our own unit fast. Additionally it also makes a slightly different rattling noise when we run our hot water.

Now I have done the following.
1. I provided our neighbors with an anti hammering device that they installed on the water supplies of the washer machine. Which didn't help.
2. I've drained our entire water system to put the air back into the risers. this didn't help either.

I'm thinking that if I installed or replace the water heater the problems will be eliminated. I'm thinking if there is a flow valve in the tank it is not working properly. It rattles when it runs and doesn't prevent the back flow when water is pulled back because of a sudden shut off . Now I don't know if a flow control is standard in a hot water tank. Also if there is a device that I can install versus buy a new hot water heater to test this theory out.

Any thoughts?