Ask Me Help Desk - Toilet and shower cause knocking inside walls?

Hello all, I really appreciate this forum and your help - I'm a newbie, first time home owner.

I own a 3 level detached, built in 1994. I have only owned it for a few months, but everything in the place is very new and well maintained.

I've noticed some knocking sounds in the walls since I moved in and believe I've tracked the source down. On our third level there are 2 bathrooms - one on suite with toilet and full bath, and one off the main hall with a toilet and full bath.

Every time my wife is taking a shower in the on suite I hear a knocking sound - it sounds just like someone knocking with a closed fist and knuckles on the inside of the walls - that lasts the duration of her shower. It's not steady, rhythmic, or constant - just random bouts of knocking.

I've also recently noticed that the toilet upstairs is starting to do the same - after a flush, and always only when flushing a --- *ahem* -- full toilet (sorry for the mental image, but may be pertinent!) - I hear the same knock noise within the walls. It also sounds louder - more violent knocking than when the showers on. Also - as mentioned before there does not ever seem to be knocking when I'm just flushing water down. Also, this toilet has always been what I would call a 'lazy' flusher - it does not perform as well as the other fixtures in the house in the sense that the water takes a while to go down, almost always gives you a slight scare that it's going to overflow, and often does not fully drain (does swirl all the way down and 'slurp' like it should).

I have these terrible mental images of the waste water pipes bursting inside the walls - you can understand that being new home owners ever slight creak or knocking sound causes us to worry.

Anyone have any advice for me? Does this issue warrant calling in a plumber or is there something I can do to figure this out?

Thanks!:confused:

Yes, the hammering is due to pipes not strapped adequately and lack of having any compression stops at the end of a water supply line in the walls. New code installations usually require a charged air tank installed near the water heater main inlet piping to cushion the water inrush when operating a faucet in the house. This is quite apparent when the clothes washing machine is running water to rinse or fill and then thumps real hard when the water flow is shut off. The only quick answer is to install a charged air tank in the line with no guarantee that the knocking stops. (loose pipes)

As for the knocking, it could also just be as simple as air in the pipes. I would open all your water taps, etc, and let them run a bit... then flush all toilets.

On the silly side... what do you do if your pipes knock?? Why you let them in! :) Sorry, couldn't resist!

That's cute - I wouldn't mind so much if they knocked out a good rhythm to hum to maybe.

So I'm feeling better about this - seems as though my thoughts of it being the drain pipe being clogged or constricted are wrong?

Is there a chance that the pipes could knock themselves to bursting or could the joints let go if the vibrate too much over time? And any chance of there being a drain issue - especially with the toilet I mean?

Did you ever get this figured out? Wondering what answer you have, if any... it will add value to this site.

Quote:

Originally Posted by Wuzizname

Anyone have any advice for me? Does this issue warrant calling in a plumber or is there something I can do to figure this out?

I don't agree with Grams explanation. There is no such thing as "air hammer". Water Hammer? Yes! Air hammer? No!
However, I like the way Nmwirez went after it. He's thinking of air chambers,( shock arresters). Most houses under 40 years of age have them. They are there to absorb the shock of rapidly closing valves and faucets, (air hammer). I'm going to give you several possible causes and solutions.
Back in the 60's we were required to to put air chambers on all bath lavatories 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 began 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.
This could also be a case of contraction and expansion.
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. Regards and thank you for rating my answer. Tom

I agree with Tom 100% and follow his first advise to begin with and I am sure you will be Ok, the second one is a bit tough to tear in to the walls and strap the pipes but if it is needed then you have to do it other wise you can live with it, FYI see the picture below to show the angle valve and the stem it is the same for all toilets and sinks, good luck.

John

Buy and install Water Hammer Arrestors... Other then that, Tom gave you great advice... Follow it...

I have the same problem a large rubbing sound when my washer starts to fill, some times when the bath room sink is turned on. I have my walls and 98% of all the pipes exposed, but can't find where the sound is coming from. It just started before I ripped into the wall. All my pipes are hanging exposed in the basement then rise up through the first floor bathroom walls, which are now open. But I can't find the source. It actually sounds like it is coming from near the water heater, boiler and main water inlet in the basement. But all the pipes there are hanging in mid air attached with straps far away from wood. There is an old water hammer arrestor right after the pressure reducing valve right by the main. I just replace the pressure reducing valve (used a watts PRV). Tuned the pressure in at 60 psi. I also added a thermal expansion tank watts plt 12, properly charged to 60 PSI, in the cold water supply just before the water heater. I also put in a new rheem fury 50 gal. although the creaking started in isolation of all these activities. It has been over a month since these updates. The only thing I can think of is the old water arrestor failed, maybe some dirt got dislodged and jammed in it. I could use some advice as the walls are open and the pipes are easy to see. Just can't really find the actual culprit.