A leaking pipe can be a water supply pipe or a waste pipe leak. How can you tell which one you’re dealing with?

The most difficult problem in determining where a leak is coming from is that often the leaking pipe is concealed and you notice the symptoms of the leak first without being able to see it. Water may be gushing or dripping through your ceiling or show water damage to your walls.

The general way to tell if it is a water pipe leak is that a water leak continuously keeps coming or it keeps dripping constantly. Occasionally, waste pipes have leaked a large amount of water into a ceiling and because it takes a long time for these larger pipes to empty out, it may feel like a water pipe leak but it is not.

One way to differentiate is by the sound of the leak. If you can locate a water pipe in the basement and put your ear to it you will hear water running in the pipe when it is a water pipe leak. Another way is to turn off all of the faucets in the home and then check the water meter in the basement. The meter should not register that there is any water being used.

Some modern meters have a setting on them that tells you if there is a water leak. If there is water coming through your ceiling, put a bucket below the leak and give it some time, if it stops then it’s most likely a waste pipe leak. If the leak continues to run, it is most likely a water pipe leak.

How do you isolate the problem when you know it is a waste leak?

When St Paul Pipeworks plumbers enter a home, there are steps they take to identify where the leak is coming from before cutting open a ceiling. They check the individual fixtures in the home to see if they can isolate which one of them is leaking. They try to recreate the leak by turning on a faucet or flushing a toilet or emptying a pail full of water into the tub to try to recreate the leak.

If the plumbers eventually have to open your ceiling up, you should be prepared for a potential mess because no matter which pipe is leaking when you open it up, more water and waste will come pouring out. The plumbers just drill one hole where they think the most water is located in the ceiling and they will use plenty of tarps and buckets to catch water and debris. That hole will allow most of the water to empty out.

How do you isolate and test surface leaks?

Other times there can be surface leaks, such as a tub or shower grout leak or a caulking leak around fixture controls. The first thing to do is to search for an access panel door, which is often located behind the bathtub in a closet.  When you open that access door and look at the piping inside with a flashlight, notice if it is wet or if there is an accumulation of water inside. St Paul Pipeworks plumbers will open the access panel to look for signs of wet areas or accumulating water, and then do a tub test by turning on the tub faucet to see if the drain at the bottom of the bathtub is leaking or if they see a leak at the bathtub waste behind the inspection door.

If they don’t see any leakage there, then they will soak various areas inside of the bathtub working from the bottom up by taking a pail full of water and dousing the overflow to see if that’s leaking. If that’s not leaking, they next go to the seam between the walls of the shower and the bathtub itself to see if they can make it leak. If that doesn’t leak, then go up to the tub spout and douse the area where the spout touches the wall with lots of water.

If that doesn’t leak, then they go up near the controls, whether it’s a two handle or a single handle faucet, and douse the handles and the cover plates to see if it is leaking through there. Finally, they conduct a visual inspection of all the grout lines to see if there are any visible cracks in the grout. Sometimes though the grout lines look good, they still may leak. St Paul Pipeworks plumbers are experienced in finding the ones that look good but are the cause of the leak. By working from bottom to top and systematically dousing all areas with a bucket of water, they usually can recreate that leak.

If you are having a problem with a water pipe or waste pipe leak in your home or are just looking for a quality plumber in the St. Paul and Minneapolis metro area, give St Paul Pipeworks a call today.


Yours Truly,

Matthew Dettwiler

Social Media Manager


How can I tell if my leaking pipe is a water pipe leak or a waste pipe leak? Ask A Plumber