Under the sink plumbing traps are often configured incorrectly. One of the most common mistakes is the S-trap configuration. First, lets discuss the importance of the plumbing trap.
The trap under the sink
The plumbing trap is used to keep sewer gases from entering into the home through the plumbing system. The graphic above is a typical drainage system under a kitchen sink. The U shaped pipe on the bottom right of the graphic is the “trap”. The pipe going from the trap to the rear of the cabinet is the “trap arm”. In this proper configuration, the U shape and trap arm form a bit of a sideways “P”. Hence the name, P-trap. When using the sink, water drains through the components and will drain through the trap and trap arm into the main stack to the sewer. After shutting the water off to the sink, water is left in the trap to keep gases in the sewer system from entering up through the pipes and into the home.
P-Trap vs S-Trap
The primary concern with the S-trap involves suction of the water seal out of the trap. The suction or siphoning can happen when a large amount of water runs down the drain quickly and there is a vacuuming action in the pipes. This may happen from the sink that you are using or another drain near the s-trap that creates the vacuum. S-traps are often found in older homes before the P-trap became the standard method. If you hear a gurgling sound after running water through the pipes, you have may an S-trap. The P-trap is the superior method of draining the sink because after the trap arm is a plumbing vent. This vent goes directly up through the roof or connects with other plumbing vents that end up going through the roof. The key here is having air behind water.
What to do with an S-trap
If you have an S-trap in your home it can be fixed by using a p-trap. However, this is not always practical as significant replacement of other drainage pipes may be required. Not all homeowners experience major issues with the an s-trap. If issues exist due to an s-trap you may have solutions. Some homeowners run a bit of water into the drain slowly after using the sink to gently refill the trap. A licensed plumber can give you an estimate to repair or replace the s-trap in your home in some cases. Plumbers may also have other solutions in dealing with s-traps in your home as every home is unique.
Lask Inspection Group, LLC
Each inspection done by Lask Inspection Group, LLC includes the plumbing system. The s-trap is something we look for in a home and will call out as a defect. Many homes exist today with the s-trap, however the p-trap is the preferred method of plumbing. Many components and systems exist in a home and the plumbing system should not be the only thing you consider when purchasing a home. It’s important to work with your realtor when deciding your home buying decisions. For your next home inspection, contact the Lask Inspection Group, LLC at 815-978-7785. Adam Lask is licensed by the State of Illinois for home inspections and is a Certified Professional Inspector through InterNACHI. Adam Lask is also a certified commercial property inspector through CCPIA (Certified Commercial Properties Inspection Association). We conduct commercial inspection throughout Northern Illinois. We serve Rockford, IL and other Illinois cities such as Loves Park, Machesney Park, Chicago, Naperville, Aurora, Geneva, Dekalb, Sycamore, Elgin, Lake Zurich, Arlington Heights, Crystal Lake, and other Chicago suburbs.
