Hi All,

Hoping someone can help with this... I have center unit row house that is 16 years old. Whenever I run the water in the upstairs bathroom there are knocking/popping noises in the walls for the next half hour. The pipes are Polybutyl, not copper (yes I know about the problems with PB piping). Also, at night the walls sometimes make a few really loud knocks. Any ideas what it is and what I can do to fix it? Thanks.

Noise from pipes can certainly be irritating. Unfortunately it is not always that easy to correct. In your case it is obviously a result of something the re-piping crew did or did not do when re-piping your house. You do not say where you are but in most states this work has to be guaranteed for a year if it was done by a licensed contractor.

Any noise of this nature requires on the spot investigation and I will not be able to help you a great deal but I will give you a few hints.

Most pipe noise is associated with loose or improperly strapped pipes or with air trapped in the pipes. Usually it is some combination of the two. It is certainly not uncommon for a re-piping job to be inadequately secured even though you have checked the wall behind the faucet that seems to cause the problem the pipe could be loose in the attic. It would help if you could pinpoint where the sound actually happens but this is very difficult.

In curing these problems you have to start by being 100% sure ALL the pipes are secure. There are devices made to help with pipe noise and sometimes it is necessary to use one to cure a problem. One is a water-hammer arrestor. It is a bulb-like fitting that has a small rubber bag inside and it acts as a shock absorber when the water is turned on or off. Old school plumbers always installed air-chambers near the end of lines or by the water heater. The air-chamber is merely a short length of pipe extending straight up from a fixture branch that will trap air and the air is supposed to act as a cushion and help with pipe rattle. These are not too reliable because eventually they fill with water but they have been widely used.

It is possible in your case that when they installed the new pipe in the wall they have loosened some wood or have some other thing in the wall that somehow reacts to the water pipe. Strictly guess work. When I have suspicion that the problem is in a certain area in a wall I will use the spray foam that you can buy at any hardware store and spray inside the wall cavity to secure whatever is in there. This will secure loose pipes and also insulate around them. You do have to use care because this foam expands and has a good deal of strength and could cause your wall to bulge if you use too much. Good idea to test the stuff before you uses it. If I have to go up higher in a wall I will drill a small hole in the wall to insert the straw sized tube that expels the foam and that small hole is easily patched. Likewise if I were crawling in the attic and suspected loose pipes down a wall cavity I could spray the foam from above alongside the hole that is drilled for the pipe to pass through.

Having said all this I would still bet that loose pipes are at least part of your problem. There are many products available to strap and secure pipes and that is what I would do first. There should be no place in your system that you can grab hold of a pipe and move it. The entire piping is required to be strapped at a minimum of from 5 to 8 feet depending on the size of the pipe.

Knocking, popping, creaking and crackling pipes are a common complaint, especially in colder weather. I can tell you what's happening and take the mystery out of it but you're not going to like the repair. When a draw is made on a hot water line the line expands against a pipe strap next to a stud and when you drain hot water from your tub or shower it goes into a chase that is a little cooler then room temperature. The heat expands the pipe causing it to rub against the stud to which it is pipe strapped. This is the sound you hear. As it cools it contracts and the noise is heard again. To repair it you must tear open the walls and locate the pipe strap that's causing the problem and shim it tight. Most people when they learn what causes it just elect to live with it. Good luck and thank you for rating my answer. Tom