How To Utilize The Pool Main Drain

I will be honest, before diving into this topic I was unsure if I even knew how to utilize the pool main drain. Sure, I know what the main drain is and how essential it is in maintaining a healthy pool. I even know how the main drain functions and where to locate it.

However, I honestly never thought about the main drain or how to utilize it any further. If you’re in my boat, this article is perfect for you.

What Is A Pool Main Drain?

Main drains and skimmers play a vital part in your pool’s circulation and health.

Despite popular belief, main drains actually do not drain anything. In fact, it’s more like a suction.

The main drain serves as one of your pool’s water outlets and is typically located in the deepest part of your pool. It uses the suction from the pool pump to pull water and small debris through the filter. It is one of the two methods your pool circulates and filters your water.

While skimmers sit near the pool’s waterline, main drains are located completely underwater. This allows all of the heavy debris to sink to the bottom and flow to the filter.

Main Drain Safety

Like most equipment that has been around for a while, main drains have evolved in style and safety. In 2007, Congress passed the Virginia Graeme Baker (VGB) Act that mandated certain safety specifications on main drains for new pool installations.

Before this act was passed, main drains were covered by a single flat grate. Ultimately, this design caused swimmers to become entrapped which ended in many deaths.

As a result, the VGB Act replaced the flat grate cover with one that is domed with openings on the sides This makes it difficult to cover all of the openings, preventing suction. More importantly, the VGB Act mandated that all public pools and newly built residential pools have two main drains.

Utilizing Your Main Drain

You can utilize your main drain to help your pool’s filtering system become more efficient. For example, if you get a ton of leaves and bugs in your pool that often float to the top, you may need more suction at the skimmer level.

Conversely, if you tend to get sand and dirt at the bottom of the pool, you may need more suction at your main drain. Additionally, if your pool water level drops below the skimmer, you can switch all suction from the skimmer to the main drain.

How To Divert Suction From Main Drain To Skimmer

To divert the suction from the main drain to the skimmer, or vice versa, you will need a diverter. Typically, you install a diverter valve in the bottom of the skimmer below the strainer basket. There should be a small arrow or pointer indicating a particular setting.

By moving the pointer arrow towards your pool, you divert the suction to the main drain and away from the skimmer. Moving the pointer away from the pool, the suction switches over to the skimmer.

During normal operation, most pool owners tend to keep the arrow pointed halfway between both settings. This splits the suction evenly between the two.