[Paul Dziw]

A year ago I had a crack and leak in our PVC waste pipe just behind our family room wall close to the first story floor. The plumber opened up the drywall and cut out the cracked portion (2 feet) which exended from just behind the family room wall down to the basement and replaced it with a new section. A few months later when it got colder I noticed that 9 times out of 10 when you flush the toilet in either bathroom upstairs I hear 2 or 3 loud bangs about 4 seconds after the toilet is flushed. The banging is coming from behind the wall right next to the PVC waste pipe just below the 2nd story subfloor. The banging is much more frequent in the colder weather. I don't believe there is a water hammer problem because I didn't notice a problem until a month or so after the plummer had replaced the section in the PVC pipe and we have lived in the house 18 years.

A few months later after I noticed the problem with the toilet flushing I began to notice that every time a hot shower is taken in either upstairs bathroom about 5 minutes later I hear a similar bang. The banging occurs one time every two minutes and this goes on for an hour after the hot shower. It is only one bang every two minutes. The sound is coming from a location next to the where I hear the toilet bang. The hot water copper pipe is located behind the wall where the sound comes from and just a foot to the right off the PVC waste pipe. It sounds like it is coming from just below the 2nd story subfloor. I am familiar with thermal expansion and the pipe is becoming longer and thicker as it heats up but it is very strange to me that the bang occurs just once every two minutes and this goes on for an hour. I also experience the same sound in the same location around 9 am every morning for a hour and then sometimes around 9pm at night for an hour or so. This has been going on every day for over a year and I would like to resolve the problem. If somebody can give me some helpful advice I would really appreciate it. Thank you!

[iamgrowler]

Is there a recirculating pump on the hot water system?

[Paul Dziw]

Is there a recirculating pump on the hot water system?

No.

[iamgrowler]

I'm going to lean towards a water hammering problem, that it occurred after repairing the break in the PVC drain is probably just a coincidence.

This is what I'm thinking:

The flapper valve in the toilet is allowing water to seep into the douglas valve of the toilet, which then causes the ballcock to fill the toilet, and the hammering sound is the result of a faulty ballcock.

Put a half a bottle of food coloring into the toilet tank and then check back in an hour or so to see if any of the food coloring has made its way into the bowl.

[speedball1]

Paul if you have a water hammer problem perhaps this will help.
.Back in the 60's we were required to to put shock absorbers,(air chambers) on all bath lavatorys and kitchen sinks. Over time water and condensate built up in them and they must be recharged. First turn off the house at the main house shut off valve. Then open hot and cold faucets at the farthest bathroom to prevent air lock.(This is important.) You will find under each fixture little brass or chrome valves. These are called angle stops. With a small pail held under the angle stop to catch the run off look under the handle of the stop and you will see a nut with the stem running through it. This is called the bonnet packing nut. Put your wrench on it and back it off counterclockwise. Now open the stop and remove the stem and washer assembly, The stop will begain to drain. When it has quit draining reassemble the stop and move on to the next one. Do this on each one of your angle stops. There will be six of them in a two bath home. When you are done, close off the faucets you have opened, turn on the water to the house, and give yourself a pat on the back.
You have just recharged your air chambers and saved yourself a hefty service call bill.

[Paul Dziw]

I'm going to lean towards a water hammering problem, that it occured after repairing the break in the PVC drain is probably just a coincidence.

This is what I'm thinking:

The flapper valve in the toilet is allowing water to seep into the douglas valve of the toilet, which then causes the ballcock to fill the toilet, and the hammering sound is the result of a faulty ballcock.

Put a half a bottle of food coloring into the toilet tank and then check back in an hour or so to see if any of the food coloring has made its way into the bowl.

Thanks. I will try the test you suggest and if such occurs replace the faulty ballcock or flapper in both toilets. If that doesn't do the trick I was thinking that maybe when the plummer replaced the section of waste pipe he raised the overall height of the waste pipe just enough so when the toilet is flushed and the water falls 2 storys and makes a 90 degree turn in the basement the shock wave is causing it to bounce off the 2nd story subfloor?

Also , any thoughts on the hot water copper pipe problem?

Paul if you have a water hammer problem perhaps this will help.
.Back in the 60's we were required to to put shock absorbers,(air chambers) on all bath lavatorys and kitchen sinks. Over time water and condensate built up in them and they must be recharged. First turn off the house at the main house shut off valve. Then open hot and cold faucets at the farthest bathroom to prevent air lock.(This is importent.) You will find under each fixture little brass or chrome valves. These are called angle stops. With a small pail held under the angle stop to catch the run off look under the handle of the stop and you will see a nut with the stem running through it. This is called the bonnet packing nut. Put your wrench on it and back it off counterclockwise. Now open the stop and remove the stem and washer assembly, The stop will begain to drain. When it has quit draining reassemble the stop and move on to the next one. Do this on each one of your angle stops. There will be six of them in a two bath home. When you are done, close off the faucets you have opened, turn on the water to the house, and give yourself a pat on the back.
You have just recharged your air chambers and saved yourself a hefty service call bill.

My house was built in 1987 can I assume that I would have these shock absorbers? Also, I don't hear the water hammer when using any of these any fixtures. It only occurs when flushing the two upstairs toilets.

Also, any suggestions how to address the other issue with the copper hot water pipe?

[Brian Croghan]

Hello Paul,

This problem does come from the main waste line. I had that banding sound in my interior walls of my house also. I lived with this noise for two years.
The banging starts when the hot or cold water is turned on in the third floor bathrooms. What happens is the hot water runs through the drains and heat the PVC. The main waste line is two close to the studs. The PVC contracts and expands when it is heated or cooled from the water temperature and the studs are pressed against the PVC causing this banging noise.
To prove my therory I cut away the stud which was two tight against the waste drain and ran the hot water only anb than the cold.
NO MORE BANGING!
My house was built in 1980 and by the looks of it every owner of this house has lived with this on going problem. I have heard almost everyone comment that this is from the water pipes banging or air pressure in the water lines.
If you can place your hand on the pipes you can feel if it is coming from the water pipes or from a drain pipe or from a vent pipe.
I hope this is helpful.

Regards,
Brian