Hi:

I have an older home with a central vacuum system. The system worked fine but I no longer get any suction.

I believe that a pipe came apart inside a wall. I confirmed this by going to the unit and cutting the pipe after a "Y" and had suction on both sides. The whole lower side works well but that is my basement.

How can I find where the pipe let go in the wall without taking down all my walls!

Any help would be much appreciated.

I seriously doubt that you have a pipe joint that has come apart. Why would it after all theses years? There is a vacuum, not pressure on the line. A vacuum would not blow a joint apart.

It is more likely that you have a blockage. Suggest running a small sewer snake down each inlet with the vacuum running. Is there any female teenagers in the house?

No female teenagers... anymore!

While doing renovations I have noticed that the vacuum pipe joints are not glued just fitted together. I have glued those that I have exposed. My wife and I also heard an unexplained clunk that we did not understand... until the suction stopped on the vacuum.

OK, with that tid bit of information I'll buy the possibility of a pipe coming loose. Suggest that with all the inlets closed , that you short across the low voltage wiring at the unit and see if you can hear air movement in the wall. Did see a month or so ago that Home Depot had a camera with a 6' cable for plumbers to look down pipes. Don't remember the price.

Before you start cutting into walls confirm that you have an open pipe. Cut the exhaust pipe, short across the low voltage control. With all inlets closed, if you have air coming out the exhaust pipe you have an opening some where. No air (or very little since you don't have sealed joints) you don't have an open pipe.

That unexplained clunk, did it occur while the unit was being used?

The clunk was not during vacuum use, we didn't associate it until a day later.

I have closed all ports and shorted the system. There is a T right at the vacuum unit. The lower half of the T is for the basement and when it is connected without the top, the suction is fine downstairs. When I connect the top T I get no suction up stairs but noise like it is sucking. I did not hear any areas where there seemed like there was sucking inside the wall. It is an older unit and is fairly loud which doesn't help with the listening.

I also hooked up my shopvac on the reverse setting and blew air into the upstairs system hoping to dislodge anything that was blocking... I found no blockage or change.

A camera may be the way to go... but I think it would be expensive.

I am thinking of listening with a stethascope to see if I can hear more through the drywall, just need to get my hands on one!

How many floors are talking about here? How many inlets? Do you have any concept of how the piping is run. Might try a drain snake or an electricians fish tape from each inlet, to see what you feel. Do you know any to get "canned smoke"?

This is probably the cheapest boroscope: Milwaukee M-Spector Digital Inspection Cameras - Borescope (http://cableorganizer.com/milwaukee-tools/digital-inspection-cameras.html)

BR200 - Video Borescope/Wireless Inspection Camera (http://www.extech.com/instruments/product.asp?catid=55&prodid=555)

This one is like $300


Terms to look for are "inspection cameras HVAC" or "boroscopes"

Some differences between some of the models are the ability to electronically tilt the head and the ability to attach hooks of various sorts to the end.