The main drain for a pool is a suction port that should be located at the deepest point on the pool floor. A main drain is responsible for aiding in the circulation and filtration of the pool water. Having a properly working and dedicated main drain line can also allow you to fully drain your pool if necessary.
Pool drains work because they have a lot of suction behind them. They pull the water down, allowing the pool to be filtered, and in the process, cleans the pool. However, this suction is the main reason why pool drains are potentially dangerous.
you can tell if your main drain is working by perhaps putting a leaf on it. If it sticks, its working. In any case though, the main drain is not why your pool is having a problem. It has nothing to do with your pool turning green.
Are Pool Drains Dangerous? Pool drains can be very dangerous. Because they have an immense amount of suction behind them in order to drain the pool and allow the water to be filtered. Because the pressure of the suction can be up to 700 pounds, if a person gets too close to the drain it can impossible to remove them.
For proper water circulation, it is best to position the flap so that it is about 2/3 closed. This will allow for more flow through the main drain than through the skimmer, which will promote a "bottom-to-top" circulation throughout the pool.
For the cleaner to operate at maximum efficiency, only the skimmer and cleaner valves should be open. So it is either main drain+skimmer or cleaner+skimmer. Never main drain+skimmer+cleaner all open at the same time.
Important: swimming pool drains are often built with short radius elbows that are normally found in cold water supply lines. These tight elbows can easily get clogged by any debris that flows past a dislodged strainer basket, and can also increase the risk that a drain cleaner gets stuck in the line.
A swimming pool main drain uses suction to pull pool water through it. Heavy particulate matter that sinks to a pool's bottom is often sucked away through a main drain.
Most of the dirt and debris that sinks exits the pool through these drains. To keep people from getting their hair or limbs caught in the plumbing, the drains are almost always covered with grates or antivortex covers (a cover that diverts the flow of water to prevent a dangerous vortex from forming).
According to the Consumer Product Safety Commission, the pressure on some pool drains can be as strong as 300 pounds per square inch. 1 This kind of pressure can suck in hair or body parts, or trap swimmers underwater and cause them to drown, even if someone is trying to pull a victim away from the drain.
When your pool skimmer has no suction, the cause is most likely a blockage. This can put the entire filtration system of the pool into question, as there will be low water pressure.
Most skimmers take approximately 25 gallons per minute (GPM) of flow for adequate performance.
It's important that pipes are buried deep so that they don't freeze. It is usually 3 to 3.5 ft deep.
Running water through the pipe will help melt ice in the pipe. Apply heat to the section of pipe using an electric heating pad wrapped around the pipe, an electric hairdryer, a portable space heater (kept away from flammable materials), or by wrapping pipes with towels soaked in hot water.
Insulate plumbing lines with blankets or towels to prevent freezing. Even pool noodles can serve as good insulation around pipes. Open all lines to ensure proper water flow. If a valve is shut off, no water will flow through that pipe, and there is the danger of freezing damage.
If there is any water left in the pipes of your pool plumbing, the water will freeze, and Physics 101 class tells us water expands when it freezes, up to 10%, and that's enough to crack pipes, pumps, filters, heaters, skimmers, and other things – that are full of water.