Hot Tub Air Blower or Venturi? Which One Do You Need?

Last updated: September 2026

Air blower or venturi? If you’re in the design stages of a DIY hot tub, it’s one of the decisions you’ll need to make before the plumbing goes in. And if you already own a tub, you may have seen both terms and wondered what they actually do.

Both put air into the water, and air is what turns a jet of water into that fizzy, bubbly massage. The difference is how the air gets there. In this post I’ll explain how each one works, the pros and cons, and which I’d choose for a block, concrete or ICF build.

How venturi works in a hot tub jet

The venturi effect is, in Wikipedia’s words, “the reduction in fluid pressure that results when a moving fluid speeds up” through a narrower section. Inside a hot tub jet, the pump forces water through a narrow nozzle at speed. Next to the nozzle is an opening connected to the air line. The fast water drops the pressure there and sucks air down the line, and the air and water leave the jet together as a bubbly stream.

The other end of the air line comes up above the waterline to an air control (an air valve) on the deck or tub edge. Open it and more air is drawn in, for a stronger, fizzier jet. Close it and you get water only. On a DIY build, I suggest one air control per side of the tub, so each group of jets can be adjusted on its own. There’s a full walk-through in How to use a venturi system instead of a blower on a block hot tub build.

Two things to know:

• It only works while the jets are running, and it works best on high speed, because the suction comes from the water’s speed.
• It gives less air than a blower. You’re limited to what the water can pull in.

How a hot tub air blower works

A blower is an electric air pump, essentially a high-speed fan in a housing, that sits in the control room. It pushes air down its own air lines into the jet bodies or into dedicated air injectors in the floor or seats. When it’s running, you get a lot more air than venturi can manage, and with air injectors you get bubbles even when the jet pump is off.

It plugs into the spa pack, and you switch it on from the topside. Balboa’s BP packs, for example, have a 230V blower output rated at 4A, with a 15-minute timer. Everything about choosing, fitting and protecting one is in Hot tub air blower: the ultimate guide.

A blower has a few downsides:

• Noise. You can hear it, especially if the control room is near the house.
• It cools the water. It blows outside air through the tub, so a long session on a cold night pulls the temperature down.
• Water can get into it. Air and water meet in the jet bodies, so water runs back up the air lines when everything stops. A blower always needs a check valve, and ideally a Hartford loop or a mounting position above the waterline too. More on that in Water in a hot tub air blower.

Blower vs venturi at a glance

	Venturi	Air blower
How air gets in	Sucked in by the water flow	Pushed in by an electric air pump
Amount of air	Moderate, adjustable at the air controls	Lots
Works without the jet pump?	No	Yes, with air injectors
Noise	Quiet	Noticeable
Electrics	None	Uses the pack’s blower output
Protection needed	Air controls above the waterline	Check valve plus a Hartford loop or high blower
Cost	A few air controls	A blower, check valve and fittings

I’m building from block, concrete or ICF: which should I use?

On a block, concrete or ICF build you’ll almost certainly use gunite jet bodies. Each one has two pipe connections: a 2in water line and a 1.5in air line. The air and water mix inside the jet body. Waterway’s gunite jet instructions cover both options. If you use a blower, “an Air Spring Check Valve… must be installed on the blower stand pipe”. If you don’t, the air intake is simply left open to the air, pointing down under a vent grate.

So both work. The air lines are the same size either way, so the choice is really about what you want from the tub:

• Choose a blower if you want the full hot tub bubble experience. Most of my customers do, and I’m a fan of them myself.
• Choose venturi if you want a quieter, simpler tub with nothing electrical on the air side, and you’re happy with a gentler fizz.

If you’re undecided, plan the air lines so a blower could be added later. It’s far easier to leave a capped tee and some space in the control room than to dig up a patio. There’s more on jet choice in DIY hot tub jets: everything you need to know and on laying out the pipework in my DIY hot tub plumbing guide.

Can I upgrade a venturi system to a blower?

In the most basic terms, yes. But you’ll need to cap off (or close) the venturi air controls first.

The main difference is that the air pipework for a blower is a closed system, so pressure builds and pushes the air out through the jets. With venturi, the air lines are open, because the air controls let the air in. If you open a valve while the blower is running, the blower’s air takes the easy way out through it. You lose pressure at the jets, and the noise goes up, which is not what you want on a hot tub.

Then treat it like any new blower install: match the blower to the pack’s blower output, fit a check valve, and get the blower, or a Hartford loop in its air line, above the waterline. My How to wire a hot tub blower covers the electrical side, and you’ll need to tell the spa pack it has a blower. See Configuring a Balboa spa pack.

Common mistakes

• Fitting venturi air controls below the waterline. Water will pour out of them.
• Running a blower into air lines that still have open air controls.
• Fitting a blower with no check valve, or mounting it low with no Hartford loop.
• Expecting venturi to give blower-level bubbles, or to work with the jets off.
• Forgetting that the air lines hold water. Drain them when you winterise. See Winterizing your hot tub.

Troubleshooting

• No air at the jets on venturi: check the air controls are open and the jet pump is on high. A blocked or waterlogged air line will also stop the suction.
• Water coming out of an air control: it’s at or below the waterline, or the water level is too high.
• Blower trips the RCD or GFCI: there’s usually water in it. Isolate the power, dry it out and fix the check valve or loop. See Water in a hot tub air blower.
• Weak bubbles from the blower: check the intake, the check valve and the blower itself. See How to repair a hot tub blower.

Planning your own build?

The air side of the plumbing is easy to get right on paper and a pain to change later. My DIY hot tub plans include the air and water plumbing layout, with the check valve and Hartford loop, plus a full parts list and the video course. The Ultimate Hot Tub Control Room Guide shows where the blower, pack and pumps go.

Blowers, check valves and air controls are available from parts4tubs.co.uk in the UK and parts4tubs.com in the USA. Not sure what you’ve got in an existing tub? Send me a picture in the comments.

FAQs

Do I need an air blower on my hot tub?

No. Venturi jets draw air in without one. A blower gives you more bubbles and bubbles on demand, but it’s optional.

What is a venturi on a hot tub?

It’s how a jet sucks air into the water. Fast-moving water through the jet nozzle creates low pressure, which draws air down an air line from an air control on the deck.

Can gunite jets work without a blower?

Yes. Leave the 1.5in air line open to the air through air controls above the waterline, and the jets will draw air in by venturi.

Can I have a blower and venturi on the same air lines?

Not with the venturi air controls open. The blower’s air escapes through them. Close or cap the air controls if you add a blower.

Does a hot tub blower cool the water?

Yes, it blows outside air through the tub. Use it in bursts on cold days and keep the lid on when you’re not in.

Blower or venturi, which did you go for? Tell me 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