How to Add a Circulation Pump to a Hot Tub (Step by Step)

Last updated: September 2026

I recently spoke to a customer who wanted to add a circulation pump to an older hot tub. It had a two-speed pump doing the heating and filtration plus some jets, and a few other pumps on other jets. The two-speed pump had become noisy, and they wanted to swap it for a circulation pump to improve efficiency and cut the noise.

It made a good video and article, so here’s a quick guide on how to add a circulation pump to a hot tub.

Why add a circulation pump?

Efficiency

A circulation pump uses far less electricity than a two-speed pump on low speed. It’s hard to put an exact figure on it, but over the life of the pump the saving is significant, especially if you run filtration for many hours a day. See hot tub energy efficiency for other ways to cut costs.

Additional heating

If you’re thinking of adding an air source heat pump or a gas heater, they work best with a circulation pump. A two-speed pump pushes more pressure than these heaters like, so it needs a bypass to protect them. A circulation pump works with them without fuss. Two related guides: adding an air source heat pump to a tub with a dual-speed pump and how to add an air source heat pump.

Less noise and wear

My customer got in touch because the two-speed pump had become too noisy and the neighbours were complaining. Pumps wear over time, and a quieter circulation pump can cut the noise and take load off the rest of the system. If you’re just trying to work out a noise, read noisy hot tub pump first.

How to install a circulation pump

Modifying a hot tub can affect the manufacturer’s warranty. That’s rarely a worry on an older tub, but be aware of it before you start. Isolate the power at the breaker before touching anything.

1. Check compatibility

First check that your spa pack can run both a circulation pump and a jet pump. If you already have several pumps, make sure there is a free output and space for the new one. Then set the pack so it treats the new pump as a circulation pump, not a jet pump, using dip switches or the setup menu. The pack needs to know this pump is dedicated to circulating the water. My video on reprogramming a spa pack shows how, and the guides to spa pack parts and programming a BP8 with a TP700 give more detail.

2. Plumbing connection

Connect the circulation pump into the same filtration loop as the existing two-speed pump. Remember the water path: pump, then filter, then heater, then jets. Check the union size on the old pump. Two-speed pumps typically have 2 to 2.5 inch unions, while circulation pumps have smaller 1 to 1.5 inch unions. See hot tub pump union sizes explained.

If you can find a circulation pump with the same union size, you can avoid cutting pipe. If the sizes differ, you’ll need some plumbing changes, such as reducers.

3. Reinstalling the jet pump

Once the circulation pump is in and the pack is reprogrammed, refit the jet pump. If you remove the two-speed pump and don’t replace it, you’ll lose some jets.

Don’t install the jet pump in line (in series) with the circulation pump, because the circulation pump would restrict its flow. Jet pumps go alongside (in parallel) with the circulation pump. Tee the jet pump into the plumbing before and after the circulation pump, so the circulation pump handles the everyday filtering and heating, and the jet pump delivers the pressure when you want the jets.

It sounds more complicated than it is. The diagram below shows what it looks like.

Common mistakes

• Plumbing the jet pump in series with the circulation pump, which chokes the jets.
• Forgetting to tell the spa pack the new pump is a circulation pump.
• Buying on horsepower alone and ignoring union size and voltage.
• Skipping the gate valves, which makes servicing a wet job later.

For sizing and more pump options, see how many pumps do you need and self-priming pump options. If you get an air lock afterwards, read how to clear an air lock.

Need a pump or a plumbing layout?

You can find circulation pumps and fittings on parts4tubs.co.uk (UK) and parts4tubs.com (USA). If you’re planning a new build and want the plumbing drawn up properly, my hot tub plans include a full plumbing layout.

FAQs

Can I replace a two-speed pump with a circulation pump?

Yes, provided you also keep or add a separate jet pump, and set the spa pack so it recognises the circulation pump correctly.

Do I need a circulation pump for an air source heat pump?

It is the usual set-up, because a circulation pump gives the steady, moderate flow these heaters like. A two-speed pump can work but usually needs a bypass.

Should the jet pump and circulation pump be in series or parallel?

Parallel. In series the circulation pump restricts the jet pump.

How big should a hot tub circulation pump be?

Small. Most are far smaller than a jet pump, but check the flow needed by your heater and filter and the union size of the pump you are replacing.

Will it invalidate my warranty?

It can on a newer tub. On an older tub it is rarely a concern, but check with the manufacturer.

Got a question about your own setup? Drop it in the comments below. I read them all.

Cheers,
Andi

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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.

Fast forward to 2025, I've helped over 1400+ 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