Repairing Your In-ground Swimming Pool Main Drain Pipe
In this article I’m assuming that you’re looking to find and repair a main drain line leak at the very bottom of your pool, and that it has a deep end. Also, I am assuming that your deepend is at least 6′ deep. This is the most common setup for pools with a main drain line here in Massachusetts.
If you have an on-ground pool like a Gibralter, the only advice I can offer you is to replace your liner, and dig up and replace the whole line while your at it. All others read on!
Diagnosing Leak In Main Drain
First thing you need to do, is verify that your main drain line is leaking. We do this by removing the main drain cover, plugging the line with a special extra long plug, and pressure testing the line. If your line won’t hold pressure, it is definitely leaking.
Repair Difficulty Level
This is an easier repair than you might think. You don’t have to replace the whole line, just repair the leak. As long as this line use to hold pressure, the leak should be within four feet of the surface or pool deck. The reason your leak will be within the first four feet of the surface has to do with the local frost line. Here in Massachusetts it only extends four feet.
The Most Common Reason For Leak
Your pools main drain line was probably not winterized properly, or the valve that locked air in the line was bad /leaky, or the plug used to lock air in the line popped out. In any case, water froze in the line, when the water froze it expanded in the plastic line and cracked it. When this happens above the ground, the pipe blows apart, often into many pieces, when this happens in the ground, it usually just puts a thin crack in the line.
Finding The Leak
First we pump water into the plugged line from the filter area, then we pump a controlled amount of pressurized air into the line. The escaping air bubbles at the cracked pipe cause a rumbling sound as the air bubbles through the water soaked ground. We stick an electronic probe in the ground, or electronic ears on the concrete deck, working from the filter area towards the pool until we hear the leak. Without an electric probe, you can stick a long screwdriver into the ground and place your ear on the shaft. Once you find the area, you simply dig it up. Hopefully, it is not under a concrete deck, or you will have to cut the deck.
Disclaimer
Pressure testing can be dangerous and should be performed by pool service experts. You risk severe injury and death when pressurizing pool plumbing lines .
Repairing The Line
Once you have the line exposed, you can make the necessary repairs. Pool Plumbing uses a minimum of schedule 40 PVC in Massachusetts. You may need special fittings not supplied by regular plumbing suppliers. Head over to your local pool store to find fittings designed for these types of repairs.
Please ask questions in the comments below, and we will answer them when we get a chance. This article was written in response to a question someone asked on Google.
