Two problems with toilet: tank filling poorly and water hammer

[jacobc]

My toilet started having two problems a couple months ago, which are probably related to each other. One, the tank is not refilling consistently. Sometimes after flushing, it just sits there. It will refill eventually, but nothing I try in terms of manipulating the levers inside the tank help with delay. Two, when it does start refilling, the pipes start making a loud knocking noise (water hammer). Interestingly, turning on the cold water (has to be cold, not hot, and can be on either the bathroom faucet or the kitchen faucet in another part of the house) stops the water hammer (it has to stay on for a few minutes). There is a sound like air gushing that I hear during the refilling too, esp. if the cold water is running and the water hammer isn't happening.

What's likely to be happening here? Is this something I can fix without calling a plumber? How do I diagnose and fix the problem?

Thanks a lot.

 

[oldognewtrick]

Have you lifted the tank top and observed the fill valve while emptying the tank?

 

[jacobc]

Yes, but I haven't seen anything that looks weird. What should I be looking for, and how would it relate to the two problems, esp. the water hammer? Thanks.

 

[oldognewtrick]

Is the float operating, can you isolate where the water hammering is coming from ( the valve or inside the wall)?

 

[jacobc]

Yes, the float seems to operating. The hammer is coming from inside the wall.

 

[user 4883]

install a rebuild kit. sounds like a valve chattering.

 

[jacobc]

I looked up "chattering valve" and did the suggested diagnostic test, and you were absolutely right, that's the cause. I'm very impressed and grateful for your help.

 

[user 4883]

I looked up "chattering valve" and did the suggested diagnostic test, and you were absolutely right, that's the cause. I'm very impressed and grateful for your help.

anytime

 

[jacobc]

Well, things have turned out to be more complicated. I replaced the fill valve. I'm confident I did it right, since the toilet is flushing and refilling, and there is no leak. But the same hammering noise starts when the toilet starts refilling after flushing. Turning on the cold water stops it, as before. So basically nothing has changed. (I'm not sure if it's refilling better now, will monitor that.)

Does this mean the problem is in the pipes in the wall? Is there anything else I can try, or is it time to call a plumber? What does the cold water stopping the hammering noise indicate?

Thanks again.

 

[oldognewtrick]

Do you have access to the plumbing underneath, basement, crawlspace?

 

[Snoonyb]

Does this mean the problem is in the pipes in the wall? Is there anything else I can try, or is it time to call a plumber? What does the cold water stopping the hammering noise indicate?
Thanks again.

Opening the cold water increases the volume of flow, so, adjusting the flow to the WC by opening the supply valve, may be the cure. Or manipulating it's volume may also.

If the valve is the older style threaded valve, (angle stop), it may be time to change it to a 1/4 turn ball valve.

 

[user 4883]

Did the rebuild kit at least solve the intermittent refill issue?
Thinking maybe a pipe clamp has come loose. See if you can get the pipes to hammer by very quickly turning full on cold and immediately shut off abruptly. Repeat a few times and let us know what you hear.