The two drains must be located between 3 feet and 6 feet apart measured from the centerline of the drain covers. The main drain piping must be manifolded at the hydraulic center.
Most pools have two main drains, but a small pool may have only one. The drains are positioned at the pool's deepest point.
An inground swimming pool's main drain is located in the deep end of the pool. A main drain circulates the pool's water by pulling water off the bottom of the pool and sending it to the filter.
During normal operation, water flows to the filtering system through two or more main drains at the bottom of the pool and multiple skimmer drains around the top of the pool. The main drains are usually located on the lowest point in the pool, so the entire pool surface slants toward them.
Main drains are not required in an inground swimming pool, however, they are strongly recommended and can be extremely useful in some circumstances. The advantages of main drains are to give you the ability to drain the water from your pool without the use of a sump pump.
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.
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.
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.
Skimmer Vs. Drain. If the pool receives a lot of leaves and other debris, more suction may be required at the skimmer than the main drain to adequately strain debris floating on the surface. Conversely, if dirt on the bottom of the pool is the principal contaminant, more suction is required at the main drain.
Pool suction drain injury, also known as suction entrapment, occurs when the drain of a wading pool, swimming pool, or hot tub suck in a swimmer's jewelry, torso, limbs, hair or buttocks. Evisceration, also known as disembowelment, could happen in case of buttock entrapment.
Slot Drain Systems offer a pool overflow drainage system that is installed around the rim of the pool. This drainage system helps manage and prevent water overflows in and around pools.
While many professionals install two returns, some prefer more as a general rule. Builder Guy Wood, for instance, often will place four returns in pools that measure 250 to 600 square feet. A vessel of 600 to 800 square feet will generally have six returns to start.
Swimming pool builders often install overflow drains near the rim of the pool that prevent flooding most of the time. If you don't have an overflow drain, or if it is clogged, it is possible for periods of unusually heavy rain to overflow your pool.
Slowly close the Main Drain valve about halfway, this is the optimal setting for vacuuming. Make sure the skim-vac did not come loose over the skimmer basket and is sealed securely over the basket. Push the pole/vac/hose into the pool and release all the air out of the hose.
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.
A single suction line is a high risk system.
No pool should ever be run on bottom drain alone due to the danger of suction entrapment and/or possible hair entanglement on the bottom or side of the pool/spa tank.
Contact between human skin and a flat pool drain can create suction equal to hundreds of pounds of pressure. In one horrific instance, four adult men were unable to pull a young girl from the grasp of a deadly drain. Swimmers can die from drowning or evisceration.
You should aim for a water level about 1/2 to 2/3 up the opening of the skimmer. Too low and you start to get gurgling sounds which are telling you that your pump is working way too hard at trying to keep the water flowing.
For me personally, I have found running around 60%-75% suction from the main drains and 25%-40% from the skimmers is adequate for proper skimming and adequate filtration.