Filter Head Gaskets
The condition where water escapes past the built in one way valve in the filter head is a major source for unexplained water loss in inground pool installations with a permanent discharge line attached to the filter. Many filter types can have this problem where a back pressure on the filter head will cause the internal gasket to shift and allow water to leak past the check valve in the filter head and drain out through the backwash line under normal pool filtering settings.
Many easy fixes are often witnessed for this condition, most commonly being a manual ball valve that prevents water from escaping into the backwash line. The downside to this easy fix is that the valve must be manually opened to backwash and manually closed afterwards.
The correct solution to this problem is to open the filter head (NOT while under pressure) and reset the gasket which will be out of its obvious position. This condition occurs when the water being pushed through the backwash line creates a vacuum after the filter is put back to “filter” from “backwash”. Changing this dial setting closes off the backwash line with a watertight seal.
The water in the backwash line is still moving however, and if there is no air gap in the backwash line (if it is full of water), a temporary back pressure is created as the water continues its path through the pipe and away from the filter. Even a small back pressure is enough to pull the gasket out of position of many models of filter.
Use this resource if you need further or more detailed information on swimming pool sand filters
Primary Leak SymptomsA leak in the filter can be elusive to diagnose. An easy check to see if your filter is leaking through the backwash line is to remove the filter sight glass when the pool is in normal filter mode. The sight glass on the filter is designed for you to view the water clarity that is being backwashed through the filter. When in regular filter mode no water should be able to access the sight glass.
The menu on the right is a chronological step by step process to determine where a swimming pool is leaking. This website is written as a readthrough technical assistance guide for locating leaks. When you believe you have identified where the pool is leaking you need to go to our sister website to see pictures and learn more about the actual swimming pool leak repair process.