A Deep Dive into all things Sand Filters

Let’s dive into sand filters and explore how they work, their key components, and a few alternative filtration mediums. Sand filters are a popular choice for swimming pools, plunge pools, and yes—even hot tubs! They’re efficient and relatively straightforward once you get the hang of them.

In this post, I’ll walk you through everything you need to know, and by the end, you’ll be well on your way to becoming a sand filter expert!

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How Sand Filters Work

Sand filters are pretty common in the pool world, but you might be wondering how they can fit into a hot tub setup. The good news is that they can, but they do require their own dedicated pump. Luckily, most modern systems use dual-pump setups, so it’s usually not an issue.

The main function of a sand filter is exactly what it sounds like: to filter water through sand, trapping debris and any other particles. 

However, one of the key parts that makes a sand filter work effectively is the Multiport Valve. It’s located either at the top or the side of the filter and allows you to switch between different modes.

The Multiport Valve

Let’s talk about the multiport valve because it’s arguably the most important part (obviously, after the sand itself). This valve gives you control over the different modes of a sand filter. Yes, a sand filter has modes, and they each serve a different purpose. Let’s break them down:

1. Filtration Mode
   This is the default mode where the magic happens. In filtration mode, water enters the filter from the bottom, passes through the sand, and exits through the other side of the multiport valve—clean and clear. The sand traps dirt and particles, leaving your pool or hot tub water nice and clean.
2. Backwash Mode
   Over time, the sand filter will accumulate dirt and other particles, slowing down the water flow. That’s where backwashing comes in. In backwash mode, water is sent through the filter in reverse to flush out all the accumulated debris. It’s simple: turn off your pump, switch to backwash mode, and turn the pump back on. Watch the little window on the filter; when the water runs clear, you’re done!
3. Rinse Mode
   After backwashing, you’ll want to rinse the filter to get rid of any leftover particles. This is just a quick clean-up step to make sure everything is set before you go back to filtration. Switch the pump off again, set the valve to rinse, turn the pump back on, and wait for clear water. Once that’s done, you’re good to switch back to filtration mode.

And that’s it! Sand filters are pretty simple once you understand how they work.

Alternatives to Sand as a Filter Medium

Now, let’s talk about a few alternatives to using sand in your filter. Do note that I’m not talking about cartridges. filters. I’ve done a video on cartridge filters versus sand filters here. 

For this article, I am referring to the medium itself. It’s worth knowing your options depending on the type of pool or hot tub you’re working with.

1. Glass
   Instead of sand, you can use crushed glass. It’s a bit more expensive upfront, but it has some great advantages. Glass lasts longer and requires less frequent backwashing. Over time, that could save you some effort and keep things running smoother.
2. Zeolite
   Zeolite is a volcanic material that’s excellent at removing ammonia and phosphates from the water. This can be a game-changer if you live in an area where algae is a constant battle. It’s also great for pools with a heavy bather load. 

The downside? It’s more expensive than sand and doesn’t last quite as long as glass—but it does outlast regular sand.

Final Thoughts

There you have it—everything you need to know about sand filters and a few useful alternatives. Whether you’re working with a pool or a hot tub, understanding how these systems work can help you keep your water crystal clear with minimal effort. From choosing the right filtration medium to knowing when to backwash and rinse, you’re now equipped with the knowledge to handle your sand filter like a pro!

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 Buildahottub.com 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