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Spinwash
October 25th, 2005, 02:59 AM
Sorry for the length....

What causes the main water line to bang (I suppose the banging is from hitting either the brick or studs) whenever toilets get flushed. It may happen on other occasions with shutting the water on and off, but I notice it the most with flushing the toilet. It is loud and at times I think it is going to come through the wall.

I manage an apartment building so this happens numerous times throughout the day. A plumber was out last spring to check on a sweating problem and checked the pressure and stated it was great.

The thing that concerns me is that prior to the plumber coming out, I had went into the crawl space to check out main line because it was sweating profusely. What I saw did not seem right at all.

The main line (copper 1 1/2" or 2" I think) extends from where it enters the building, approximately 25' to 30' to where it disappears behind the wall and rises approximately 4'. The pipe is only supported by two pieces of plumbers tape, spaced about 10' apart.

My first thought when I looked at the pipe is that it was pulled from the deep depths of the ocean or something from the Titanic. It looks like someone has been beating the pipe with a crow bar. Another thing that looks out of place is hanging tape support for the pipe before it disappears behind the wall is actually hanging at an angle and has cut into the pipe. The strap has gouged into the pipe and if it wasn't for the thickness of the supply line, it would have burst by now. Pretty obviously the pipe has been whipped from side to side.

I guess I have two questions. Why does flushing the toilets cause the pipes to bang so loudly? (by what I saw under the building, my guess is there is probably very little supporting it inside the wall). The banging over the last couple of weeks has been more intense.

Second seems to be common sense, but the pipe entering the building can not be to code. The pressure has already been checked on the line and found to be good (I explained to the plumber what the pipe looked like in the crawl space). The building took on new owners just after the pipe was checked for the sweating. I was told to leave the pipe alone (among the suggestions from the plumber was to insulate the pipe) by the owners.

The new owners have forked out a lot of money in the last several months for various repairs. I mentioned to them the issue but with everything else that has happened, I am sure its been overlooked. I don't want to bring it to their attention again if it is not as bad as it looks, but at the same time I want to save them a costly repair bill should the pipe decide to burst in the middle of winter. The banging over the last several weeks has been more intense and actually shifted from where I used to here it bang. Should I bring this to their attention again or am I reading more into the problem that I should ?

Again, sorry for length/being overly descriptive.

Thank you in advance for recommendations.

Mike

DUNBAR PLUMBER
October 27th, 2005, 03:54 PM
http://www.wattscanada.com/faq/regulators/main.html



That link above answers it all. If no one put a pressure gauge on the water lines, not even the plumber knows what good pressure is.


Sounds like a PRV and Expansion tank are in order to correct the problem. Fast closing valves are notorious for sending warning signals when loud fast banging are an issue. Everything in your home is designed/engineered for 60 pounds; most cities/states require protection after 80.


It could be as simple as reworking the support of the piping but 90% of the time the symptom marks the issue of a bigger problem.



Read the complete link top to bottom to understand what is going on.

Spinwash
October 28th, 2005, 10:32 PM
Thanks for the info, I read the link. I did forget to mention we have a pressure regulator value on the line and the plumber said we were at 60 lbs when he measured it. So I don't think that is the problem. One more question. The pressure regulator value is located just a few feet before it enters the hot water heaters and the cold water lines that branch off to supply the apartments. The supply line runs from the street approximately 75' before it gets to the pressure regulator value, making bends and turns through walls, etc. Would this make a difference? All the banging/knocking of the pipes occurs before it hits the value.

Thanks again,

Mike