Plumbing in the Home/Sudden drain leak


Drain Pipe
Drain Pipe  
QUESTION: Hi Thomas,

We have a finished walkout basement with bedrooms on the walkout side.  We went overboard protecting it from possible water leaks.  The insulation in the basement is polyurethane spray insulation that covers much of the piping in the exterior walls.  

We found a sudden pool of water in the carpet under the clean out access area located in the room next to the concrete wall of the home.  It was a lot of water all at once.  It appears to be a drain leak.  When we pour water down the drain little trickles of water seep out around the area where the drain clean out is in the pipe.  Interestingly, when we turn the water back on but do not use any of sinks/toilets connected to the drain pipe - it gets a very small drip of water in the same area.  Wondering if the pressure in the lines when turning the water on creates this - or if there something related to the water lines?

We live on a hill and our septic drains down from our home.  There has been a lot of rain lately and one of our neighbors had basement water when they had not had it in the past.  This summer we were due to have the septic pumped once we had dry enough weather.  Last summer we noticed green around the septic during the drought.  It's been 8 years and no pumping with a large family.


l.  Could a sudden leak causing this much water all at once to pool be caused by septic overload due to the excess rain?  This is the only area in the house having an issue.

2.  Since I cannot access the entire drain pipe due to the polyurethane insulation, is it more common for drain pipe leaks to leak near the clean out?

3.  The plumber suggested we try to locate the leak first before having to pay him to do so.  Is the only way to do this to remove all the drywall and chisel out the polyurethane insulation?

Thank you for your response.

ANSWER: Dear Rachel,

   The process of troubleshooting leaks can be a tricky one.  One of the first things that I do is to consider all possible sources of the water and eliminate them one by one.

1. Could the water be coming in from outside the house.... like rain or ground water?  Can it be coming through the walls?

2.  Is it an area of the house that has frequent use?  Can you accurately determine when the water first appeared?

3.  Are there water supply lines in that part of the house?  Are any on that same wall?

4.  Is there a bathroom directly over the area?

   The foam insulation is a good product, but like everything else it has downsides too.  The moisture could be travelling between the exterior wall and the polyurethane.  Because of the characteristics of the polyurethane.... (there can be air pockets and channels or grooves between the foam and the wall) it would be possible for the water to travel a long distance before emerging on the floor of the basement.

    Because it seems to have appeared suddenly and then seems to trickle I wonder if you were using an outside faucet.  I have often encountered "Frost Free" spigots which had been left with a hose connected through the winter... the hose prevented the spigot from draining completely so that it froze and broke inside the wall or basement.  The leak does not show up until the faucet is used because of the way it is designed... but because you are outside when it is used it is not easy to notice when it is leaking.

---------- FOLLOW-UP ----------

QUESTION: Thank you, Tom.  This was very helpful.  I decided to try to rule out the leak by coloring the water and pouring it down the drain to find the source of the leak.  Sure enough it was the drain pipe - cracked above the area of the clean out.  What was confusing was the extra water draining into it when we were not using the drain for anything.  That's what made us wonder if there was a leak in a water line. Here - our plumber did not run the drain line for our ice maker outside to the house as it was designed to do (model we had purchased) and he instead ran it into the garbage disposal (which is still okay).  We just knew we had an extra drain pipe sticking outside the house for the ice maker - so didn't immediately think of the ice maker creating the extra clear water that was flowing through the drain.

Although we have removed the drywall and we're not seeing very little evidence of mold/mildew - just wet dry board, the drain itself (only 1 of the 3 sink drains draining into this drain pipe) has a really bad smell of mildew coming from it.  The septic has been recently pumped - so it's not that.  What could be causing this - and why would the same odor not be coming from the other sinks that share the same drain pipe?  The sink drain with the odor is in the island so it must 90 degree over to the wall toward the other sinks and drain pipe.  That's the only difference.  Any thoughts?

Dear Rachael,

  Being that the sink you are having concern about is on an island there are two factors that can cause the odor you mention.  First, there may be no vent close enough to properly serve the trap... thus, water may be getting siphoned from the trap and allowing gasses (odors) to escape.

   Second, the pipe from this drain needs to travel horizontally for a distance before connecting with the rest of the drain system.  Any horizontal section of pipe will provide the opportunity for buildup to develop.  Those waste particles of food, grease and even soap stick to the pipe and decompose there.  The gasses from the decomposition need to go somewhere, and if there is no vent available they can eventually make their way through a trap.

   There are foaming drain cleaning products that can help with this.  However, since you have a septic system I would recommend that you don't use chemicals like that.  I have always preferred to use products which use natural bacteria and enzymes.  You add this you your sink along with a little water at night when the sink won't be used for a while.... that allows the little "Pac-Men" to eat up any buildup that is in the pipes.  Afterwards they get flushed into the septic system and help it to function better.  

Plumbing in the Home

All Answers

Answers by Expert:

Ask Experts


Thomas Ambler


I am experienced at troubleshooting and solving all types of plumbing problems. Issues related to specific manufacturers fixtures and specifications though are beyond my field of expertise. I have dealt with problems in both rural and urban areas, and with water supply and drainage systems. Plumbing issues can be very obscure... such as odors, stains or occasional seepage. I have even had to chase rats from a customer's sewer line.


I have 25 years experience dealing with plumbing systems (which also includes hot water and steam heating systems). My main expertise is in diagnosing and solving problems. I have worked in construction and installation of new systems but do not regard myself as an expert in that area.

Asbury Park Press, Seattle Times, Denver Post.

I completed high school and one year of college. I served 4 years in the Marine Corps and have education in electronic and electrical troubleshooting and repair. I have attended classes on installing and repair of oil burners, and I have EPA universal certification for air conditioning and refrigeration. I am now enrolled as a full-time student at Everest college to re-train for a new career. Any donations of financial support would be greatly appreciated.

Past/Present Clients
All of Denny's Restaurants in NJ, Several Burger King stores, I have done work at two different homes for Bruce Springsteen. I have also worked for Jim Johnson (of J&J) and his family, Whitney Houston, Steve Forbes and many others.

©2016 All rights reserved.