Installing a Main Drain for Your Hot Tub or Plunge Pool

Installing Main Drains

Installing the main drains that you are going to need on your hot tub or plunge pool is probably for most going to be the first bit of plumbing you do.

They need to be installed when you pour your slab or your base so in this article and in the video blow, I explain everything you need to know about the installation of the main drains.

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What is a Main Drain and Why Do You Need It?

A main drain is a crucial component of your hot tub or plunge pool’s plumbing system. It’s typically 5 to 8 inches in diameter and comes in pairs that connect together in a tee configuration. This ensures that if one drain gets blocked,the other one can still function. This is a safety feature required by the Virginia Graeme Baker (VGB) Pool and Spa Safety Act.

Did you know that in the United States, there were an estimated 360 unintentional drownings involving children in spas and hot tubs from 2010 to 2014, according to the Centers for Disease Control and Prevention (CDC)? The VGB Pool and Spa Safety Act was introduced to prevent these kinds of accidents. A main drain is just one of the safety features required by this law.

Installing Your Main Drain

The key takeaway is that you need to place your main drains in position before you pour the concrete pad for your hot tub or plunge pool. This is because the pipes will be buried beneath the concrete.

Here’s a step-by-step guide on how to install a main drain:

  1. Dig the trench: If you plan on installing a hydrostatic release valve and collector rod, you’ll need to dig a trench to accommodate them.
  2. Position the main drain: When positioning the main drain, consider the final thickness of the concrete slab. You want the finished level to be flush with the surface once you add the drain cover. Builder Hot Tub recommends looking for the grate or grill that connects to the drain to determine the finished surface height. Getting this right is important because if the drain is positioned too high, it will be unsightly and create a tripping hazard. If it’s positioned too low, the grate won’t sit flush with the surface.
  3. Pipework installation: Use at least 2-inch diameter pipes for the main drain. Remember, it’s always easier to decrease suction later with a ball valve than it is to increase it.
  4. VGBC compliance: Ensure your chosen main drain complies with the VGB regulations. Look for brands like Major Culprit, Waterway, CMP, Pentair, Hayward, and CertainTeed. These brands typically have dome-shaped drains, which are a VGB requirement. You’ll also need two drains, not just one, to comply with these safety regulations.

Main Drain vs. Jet Drain

Main drains are not suitable for the jet systems in your hot tub or plunge pool. They simply aren’t designed for the high water flow required to power the jets. Instead, you’ll need super high flow suction drains typically installed in the hot tub walls. These can handle up to three times more water flow than a regular swimming pool drain.


Installing a main drain is an important step in building your hot tub or plunge pool. By following these steps and using the right materials, you can ensure a safe and functional plumbing system. If you have any questions about installing a main drain, feel free to get in touch – always happy to hear from you.

Can I Help You?

If I can help you in any way I would love to hear from you. You can get in touch using the form below.

Thanks - Andi


Hi, Andi here. I own and also write all of the articles and info pages on the site. Some years back now, I built my own hot tub but struggled to find the information I needed. So, once my tub was complete, I started this website to help others in their own pursuit of hot tub and plunge pools DIY building information.

Today, I've helped over 1000 DIY customers just like you all over the world build hot tubs and pools. Have a good look around the site, there are lots of resources here. Please do get in touch if I can help you. - Cheers, Andi

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