The source of an underground water leak can be hard to diagnose. In some cases a sewer leak can be mistaken for a water service line leak resulting in unnecessary and costly work being mistakenly performed. In this post we will explain when a sewer leak test, also commonly called a sewer dye test, is appropriate before underground plumbing work is commenced. We will also explain the particular circumstances when a dye test is a good idea.
How can a sewer line leak appear to be a water leak?
Bear in mind that frequently fresh water and waste water can appear virtually alike. This is most prone to occur when the waste water in question is composed primarily of rain water. Although it is not a common occurrence, there are two primary cases when a leaking joint on house drain line can seem like a broken water service line:
A hung house sewer or house drain
A hung house sewer is what is referred to when the house drain in a basement is above the finished grade of the basement floor. As house drain pipes get older the joints can leak causing water to leach out. This can particularly happen on older clay house sewers when cast iron pipe from the inside of the house is slid inside of clay pipe outside the house.
In these cases the joint was usually just some concrete which can wear away over the years. When a house drain is above a finished floor of a basement and the joint leaks the water can readily appear as if the water service line is broken.
If the house sewer is blocked even more moisture can appear making a water line leak seem all the more plausible – yet incorrect. All that may be needed is a cleaning of the pipes. If after a cleaning the sewer leak continues then a sewer repair will be needed.
A house drain or house sewer raised above finished grade
In some cases such as a house on a hill ( a structure above the finished grade of the sidewalk or roadway) a leaking pipe joint can make water appear that seems just a like a water service line leak. If at some point the house sewer is above the finished outside grade waste water can actually come out of the ground.
This would be particularly prone to happen if the waste water was under pressure from the sewer being clogged. This occurs because water naturally seeks it’s own level.This is another case where all that may be needed is a sewer cleaning and it does not mean your sewer or water line is broken.
When is a sewer dye test a good idea?
In many cases, particularly the two mentioned above, a sewer leak test (sewer dye test) can avoid unnecessary and costly work that will serve no purpose. Many homeowners and experienced plumbers alike have been fooled by water running above ground or on a basement floor into assuming it is from a water service line. In some cases a complete water main replacement was performed only to discover the same exact leak after the service line was turned back on. Though it is hard to fault either party when such a tricky situation arises, a sewer dye test could have avoided the error and a potential dispute.It should be noted that a sewer dye test is not complicated and can be performed by virtually anyone. The cost of most acceptable dyes are just a couple of dollars, and no special tools are needed for the sewer leak test itself
What is a sewer dye test?
A dye test may sound much more complicated than it actually is – it is not like some complicated medical procedure! Many items can be used as a dye including food dye or clothing dye. Some people have actually used milk as a dye to make the water cloudy white when it leaks out – and it worked. However the preferable item to use is a concentrated dye made specifically for this purpose. A very small amount of this dye, perhaps 1/2 an ounce, will clearly and readily appear if sewer water is leaking out from a house sewer or house drain.
A dye test is started when dye is placed into the drain system. If the test is for the pipe outside the house it is best to open the house trap – but make sure it is not backed up first or you could be inundated with waste water. You can also place the dye inside a toilet bowl and flush a few times of place it in a sink and run the water. But as stated the trap is the ideal spot because it is closest to the front of the basement wall. Once placed in the drain system if there is a sewer leak the dye should appear in a few minutes. In some cases, such as when it has to travel through the ground a distance, it may not appear for a couple of hours. If dye does appear it is a clear diagnosis of a sewer line issue that eliminates the possibility of a water line leak.
Even if a licensed plumber is asked to perform a dye test the cost is minimal. A lot depends on the job location from the plumbers office and what city or town you are located in. But regardless of the cost, this test can save thousands of dollars in misdiagnosed plumbing repairs or water main replacement costs.