Hot Tub Air Blower: The Ultimate Guide to Choosing, Fitting and Protecting One

Last updated: September 2026

A hot tub should be hot, but when most of us picture the perfect soak, it’s not just the heat. It’s the bubbles. So where do those bubbles actually come from? In most tubs, the answer is the air blower.

This guide covers what a hot tub air blower does, how to choose one, how to wire and plumb it into a DIY hot tub, and how to stop the one problem that kills more blowers than anything else: water getting into it. Bookmark it, because you’ll probably come back to it when you get to the control room stage.

What is a hot tub air blower?

A hot tub air blower is a small electric air pump, essentially a high-speed fan in a housing. It sits in your control room and pushes air into the tub through a separate set of air pipes. It doesn’t touch the water itself, and it must never get wet.

Blowers come in 120V and 240V versions in the USA, and 230V in the UK and Europe. Which one you need isn’t a matter of preference. It has to match the blower output on your spa pack.

How does a blower work?

In a DIY hot tub, whether it’s block, concrete or ICF with gunite jets, the blower connects to air pipes (I use 1.5in) that run to the jet bodies or to dedicated air injectors. When the blower runs, it pushes air through those pipes and into the jets, where it mixes with water that the jet pump is already pushing through under pressure.

That air and water mix gives you a bubblier, fizzier jet and the familiar rolling bubbles of a hot tub. It’s a touch of luxury that makes all the effort worthwhile. There’s more on how the air and water sides fit together in my DIY hot tub plumbing guide and How to install gunite jet bodies.

Do you even need one?

Not always. Venturi jets draw air in from the surface without a blower. They’re quieter and there’s nothing electrical to get wet, but you get less air. I’ve compared the two in Do I need an air blower or can I use venturi?, and there’s a build example in How to use a venturi system instead of a blower.

Choosing a blower

Match the spa pack first

The blower plugs into the spa pack, so the pack sets the limits:

• Voltage. Balboa’s UK and European BP packs have a 230V blower output. In the USA, check whether your pack’s blower output is 120V or 240V and buy to match.
• Current. Balboa’s BP8 tech sheet rates the blower output at 4A maximum. At 230V, that’s about 900W, which lines up with the 900W or so I’ve always suggested.
• Timer. Most packs switch the blower off automatically after a set time. It’s 15 minutes on the BP packs.

What size?

A good rule of thumb is a 1–2HP blower. Most residential spa blowers fall in that range. For example, the residential blowers on parts4tubs.com run from 1HP to 2HP in 115V and 230V versions. If your control room is a long way from the tub, or you have a lot of air injectors, go towards the top of that range, as long as it stays within the pack’s rating.

Brands

Blowers come in plenty of types, sizes and brands. LX, Ultra, Balboa, Hydro-Quip (Silent Aire) and Air Supply are common. Most will perform well if they’re matched to your pack and plumbing. A “silent” model is worth the extra if your control room is near the house.

Where to mount the blower

This decision matters more than the brand. Hayward’s spa blower installation manual says to install the blower at least one foot (305mm) above the maximum water level, in a well-ventilated place free of debris, chemicals and sprinklers. It needs a free flow of air for cooling, so don’t bury it in a sealed box.

In a DIY tub, the control room often sits lower than the waterline, and that’s where the trouble starts. When I remodelled my own control room, I moved my blower up onto a shelf with the air line running above the waterline. There’s more in My hot tub control room remodel and Hot tub control room position.

Connecting the blower: power

The blower plugs into the spa pack, which is the control unit that runs the heater, pumps and blower. On the topside control, one button turns the blower on and off.

On a Balboa pack, the blower connection is a pinned AMP-style plug. Depending on the make of your blower and pack, you might need to change the plug on the blower to match. It’s not a difficult job, but get the pin-out right, and do it with the power isolated. I’ve covered it step by step in How to wire a hot tub blower, and the bigger picture is in Hot tub wiring explained.

Then set the pack up. The pack only knows it has a blower if you pick a setup number that includes one. See Configuring a Balboa spa pack.

Connecting the blower: plumbing

Blowers generally come with one of two connections:

• A socket (1.5in or 2in). This is the simplest. You glue the air pipe straight into it with PVC solvent cement. There’s a guide to doing that properly in How to make the perfect PVC solvent weld joint.
• A union nut and tailpiece that screw onto the blower. You may need reducers to get to your pipe size.

Here’s a typical example: a 32mm union nut onto a 1in tailpiece, trimmed to fit, then a 1in to 1.5in reducing bush into a 1.5in check valve.

On pipe size, I run 1.5in air lines. Hayward’s manual suggests a 2in supply line from the blower, reducing to 1.5in at the tub, which is worth doing on longer runs. Keep the run as short and direct as you can, because every metre and elbow takes some push away from the bubbles.

Keeping water out: check valve and Hartford loop

This is the most important part of the post. Your 1.5in air pipes and 2in water pipes might look separate, but they meet inside the jet bodies. When the pump and blower stop, water flows back up the air lines until it’s level with the water in the tub. That’s normal. What you have to stop is that water getting any further, into the blower. A wet blower trips your RCD or GFCI, corrodes the motor, and can even slowly drain the tub.

1. A check valve (always)

A one-way check valve lets air out towards the tub and closes when the blower stops. It’s not optional. Waterway’s gunite jet instructions say an air check valve must be installed on the blower line. Hayward adds that it should be fitted vertically, somewhere you can reach it for servicing, above the water level.

2. A Hartford loop or a high blower (as well)

Check valves can stick or weep, especially with a lot of water pressing on them. This is where gravity comes in.

Rob, who built his own hot tub in France, had exactly this problem. His blower sat below the waterline, and water was getting past the check valve. His fix was a Hartford loop: the air line rises up above the waterline in an upside-down “U” before dropping back down to the blower. Water can’t climb above the level of the tub on its own, so it can’t get over the top of the loop to the check valve or the blower. It’s a simple fix, and it doesn’t rely on a part that can wear out.

Hayward’s manual puts the loop at least one foot (305mm) above the water line. Allow for the level rising when people get in. Keep the check valve as well, so the loop and the valve back each other up. I’ve gone into this in more detail, with a diagram of both options, in Water in a hot tub air blower.

On a new build, do both from day one: a check valve, plus either a blower mounted above the waterline or a Hartford loop. It’s a few fittings and a bit of pipe, and it’s far easier before the control room is boxed in. My plans show the loop for exactly this reason.

Blower troubleshooting

Symptom	Likely cause	What to do
RCD or GFCI trips when the blower runs	Water in the blower	Isolate the power, remove the blower, empty it and dry it. Then fix the check valve or loop. See water in a blower and breaker tripping.
Button does nothing	Pack setup has no blower, wrong pin-out, or a blown fuse on the board	Check the setup number, then the plug, then the fuses.
Runs but weak bubbles	Blocked intake, stuck check valve, water still in the air lines, or an undersized blower	Clear the intake, check the valve, and give it a minute to push water out of the lines.
Switches off on its own	The pack’s blower timer, or the blower’s own thermal cut-out	Timers are normal. If it cuts out early, check its ventilation.
Hums, rattles or screams	Worn bearings or a damaged motor	See How to repair a hot tub blower, or replace it.

One more thing people don’t expect: blowing outside air through the water cools it. On a cold night, a long session on the blower will pull the temperature down, so use it in bursts and keep the lid on when you’re not in.

Common mistakes

• Buying a blower for the wrong voltage, or one that draws more than the pack’s blower output allows.
• Mounting the blower on the control room floor below the waterline, with no loop.
• Leaving out the check valve, or fitting it where you can’t reach it.
• Putting the blower in a sealed box with no ventilation.
• Forgetting to change the pack’s setup to include the blower.
• Forgetting the air lines when winterising. Water left in them can freeze. See Winterizing a hot tub.

Planning your own build?

The air side of the plumbing is easy to get right on paper and a pain to fix later. My DIY hot tub plans include the air and water plumbing layout, with the Hartford loop, and a full parts list. The Ultimate Hot Tub Control Room Guide shows where the blower, pack and pumps go. Replacement blowers and check valves are available from parts4tubs.co.uk in the UK and parts4tubs.com in the USA.

Want to know more about the jets the air goes into? See DIY hot tub jets: everything you need to know.

FAQs

What does a hot tub air blower do?

It pumps air through separate air lines into the jets or air injectors, where it mixes with the water to make bubbles. It doesn’t heat or move the water itself.

What size blower do I need for a hot tub?

Usually 1–2HP. It must match the voltage of your spa pack’s blower output and stay within its current rating, which is 4A (about 900W at 230V) on Balboa’s BP packs.

Where should a hot tub blower be mounted?

In a dry, ventilated place, ideally at least 300mm (1ft) above the waterline. If it has to sit lower, run the air line up in a Hartford loop above the waterline, and always fit a check valve.

Do I need a check valve on a hot tub blower?

Yes. Water runs back up the air lines whenever the blower stops. A check valve is the first line of defence. A Hartford loop or a high blower is the second.

Does a hot tub blower cool the water?

It can. It blows outside air through the water, so long sessions on a cold night will lower the temperature. Use it in bursts and keep the lid on.

Can I use a 120V blower on a 240V pack?

No. Match the blower to the pack’s blower output voltage. Check the label inside your pack’s lid or its tech sheet.

Got a blower question I haven’t covered? Drop it in the comments below. I read them all.

Cheers,
Andi

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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