During winter months or periods of non-use, most pool drains do not need to be plugged, but in some cases plugging a main drain is required or recommended. Plugging a main drain shuts off the suction caused by the drain and prevents water from traveling through the lines connected to the drain.
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. This is useful when replacing your pool liner.
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.
Should the Pool Main Drain be Open? No, not if you are using a suction type of cleaner. The purpose of a pool main drain is to pull water from the bottom of the pool through the pump and filtration system.
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.
Main Drain: The main drain is typically located at the deepest point of the pool and is used to lower the water level, however its primary purpose is to circulate water from the bottom of the pool. It is recommended that about 1/3rd of the circulated water come from the main drain.
The main drains are usually located on the lowest point in the pool, so the entire pool surface slants toward them. Most of the dirt and debris that sinks exits the pool through these drains.
Most pools have two main drains, but a small pool may have only one. The drains are positioned at the pool's deepest point.
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.
The first thing to do to increase the suction is to check for blockage and air leaks. If one of the skimmers does not suck, it would be necessary to remove the basket from the skimmer. Then check if there isn't a flow control valve at the bottom of the skimmer, which would be almost closed.
In order to tell if the valve is open or closed, the general rule is, if the handle is switched 90deg to the flow, it is off. As you can see from the diagram above, if the handle is in line with the flow path, it is on. Simple.
So, if you see that you pressure quickly drops to 2 psi, it's likely that there's a leak in the main drain line somewhere between 4′ – 5′ under the water level of the pool. If there is a leak in the section of the line at or above the water level of the pool, you'll see a quick drop to 0 psi.
When constructing a new swimming pool, if you are going to use a main drain it is required that you use two. This is due to safety regulations to help prevent Main Trap Entrapment. Main drain entrapment occurs when the suction is so great through a single main drain that a person can become stuck on or in the drain.
(Use chemicals as labels indicate.) Use 1 gallon of liquid chlorine per 10,000 gallons of pool water. Clean liner above the water line with Swimway Tile & Vinyl Cleaner or another product.
Closing a pool that is green with algae, or dirty with debris or with water that is unbalanced, leads to heavy staining and saturation of the water with dead algae cells, which makes it easier for subsequent generations to grow.
Often, it will look something like this. 12.5% Liquid Chlorine Pool Shock – Normal Dosage: 1 gallon of shock per 10,000 gallons of water. Shock Dosage: 2 gallons of shock per 10,000 gallons of water.
Drain the water down to no more than 6 inches from the bottom of the skimmer if you plan to use a standard floating winter cover. Use your pool filter, switched to the "Drain" setting, to empty the pool water.
3. Single Drain - Not Unblockable - means there is a single drain which can be sufficiently blocked by a human body to create a suction hazard. This type of drain must be protected by an approved safety vacuum release system or other equally or more effective system.