Welcome to Just Answer,
Assuming this is a fairly new pressure balancing valve (faucet) the problem you describe requires a specially designed cartridge that is made specifically to resolve this issue. I'm assuming the banging is rather rapid and occurs while the water is running. The manufacturer should supply the replacement part at no charge
is presure balancing valve just under the cover it is white with the handle sticking out of it
If my description of the rapid banging is accurate you need the part I described above
ok but I need to know which part to take out. yes rapid banging but only when hot water does not come in fast enough, if you back of the cold water the banging stops.
You need to replace the entire cartridge inside the valve. You will need the model of the valve then you could try a plumbing supply house that sells AS or call American Standard directly. While this problem is uncommon it is a known issue and a specially modified cartridge is needed to fix it
I took off presure valve and ran water and it still comes in slow. so problem cant be with presure valve
has to be undernieth?
What do you mean "I took off the pressure valve"?
I turned of the water, took the cover off and then removed 3 skrews from the valve and removed it. then i turned on the water to see the water presure , hot was low and cold was fine.
If you removed the cartridge and the hot water flow is poor coming out of the valve body then you probably have a blockage in the line feeding the valve or in the valve body
hmm to I need to replace the whole valve. of does the part undernieth come out off also. rick
is the body valve replaceable?
there is a brace plate with tree skrews I took off also, does this hold the valvebody?
When you removed this stuff did the water come out of the shower head or out of the wall?
no the shower head was disconncect because i took of the faucet. it came out of the valve in the wall
The valve body is the cast brass fitting that the water lines connect to. When you remove the cartridge completely you should be able to see the internal openings in the valve body. You can replace the entire valve not just the body.
You may be able to re-use the trim
Are you sure there are no shut offs in the line or at the valve inlets that may be partially closed
no water works in the sink right next door just fine. not sure what you mean by trim?
The handle, the escutcheon
Are there small valve stems with slots on the end where the water pipes connect to the valve?
there is a brace plate I just took off under it is a grey plastic part with three holes. should I try to take this out
Yes. If this isn't out then your flow test means nothing. All the guts need to be out of the valve
I mean brass
You need to remove everything All the guts) from the valve body
ok Just took grey part out. did not come easly there white vavle with two holds underneith wont easly come out. I gues I can force it?
All the plastic parts are removable. How you get them out is your risk
of course. I will have to replace the whole thing anyway if this does not work. let me try
ok got it out. not easy probable some damage, lots of corrotion inside it and behiind it. that is why it would not come out. is this part easy to replace.
You haven't told me which model valve you have so it's difficult to say for sure. Most AS valves are pretty easy to fix
not sure of model is it on the presure valve. what is AS mean
American Standard. What you may see on the valve guts are part numbers not the valve model.
dont know, but I should go to plumbing supply store. or you think it has to be specifically american standard.
It has to be specifically American Standard if you want parts or want to use the same trim. If you are going to replace the entire valve any brand will do as long as the escutcheon (trim plate) covers the hole in the wall.
Do you have any more questions?