DIY Hot Tub Jets: Types, How Many You Need and How to Size the Pump

Last updated: September 2026

DIY hot tub jets are so important. The bubbles. The massage. For me, the whole “hot tub” experience comes from the jets. It’s the part of the build you really want to get right, because once the walls are rendered and tiled, the jet bodies aren’t going anywhere.

In this guide I’ll go through the options for jets in a DIY tub, clear up some of the confusion, and answer the questions I get asked most often.

Do I need jets in my tub?

This really comes down to personal preference. For me, the jets are part of the whole experience. If you don’t have jets, you really have a soaking tub rather than a hot tub. That’s my humble opinion, of course. And if you’re going to the trouble and expense of building a hot tub, surely you want it to be as good as it can be? I’ll let you decide on this one.

If you do go without jets, you still need returns, the fittings that send heated, filtered water from the heater back into the tub. Just so we’re clear: swimming pool returns are not jets. They move water gently to circulate it. They won’t give you a massage. A cold plunge or a simple soaking tub is a good example of where returns alone are fine. See How to build a DIY cold plunge pool.

How do hot tub jets work?

A hot tub jet mixes water and air and fires the mixture into the tub. Water comes from the jet pump. Air comes either from a blower (a fan that pushes air down its own pipework) or by venturi, where the fast-moving water pulls air in through a pipe that’s open to the atmosphere. The two only meet inside the jet body, just before they leave through the jet face.

The pump’s flow is the engine. The air adds volume and bubbles, which makes the jet feel much stronger. Run the pump on full with the blower off and the jets are good. Switch the blower on and you really notice the difference. Not sure which to choose? Read Do I need an air blower or can I use venturi?

The internal (the part you see and touch) decides how the water comes out. Some are fixed. Others let you turn the face to reduce the flow, so each person can set the intensity they like.

Types of jet internal

Internal	What it feels like	Good for
Directional	A single, focused stream you can aim	Lower back, feet, targeted spots
Roto	A spinning stream that sweeps in a circle	Broader back massage
Twin roto	Two rotating streams, a pulsing feel	Shoulders and upper back
Massage	Several smaller streams from one face	A gentler, spread-out massage

Waterway also lists Multi Massage and Galaxy internals for the Poly Storm thread-in jet, and its installation instructions rate every one of them at 10 GPM. So you can mix types around the tub without upsetting your flow calculation.

Are they the same as the jets in a shell hot tub?

The jets we use in block, concrete or ICF tubs are a little different from the ones in plastic shell tubs. They might look the same from the front, but the bodies behind them aren’t.

• Block, ICF and concrete tubs use gunite jet bodies. The body is set into the wall with pipe stubs sticking out, then the wall is rendered and tiled around it, and a wall fitting and internal go in at the end. I’ve covered this step by step in How to install gunite jet bodies in a DIY hot tub.
• Stock tank and wooden tubs use the same style of jet as a shell tub. You drill a hole through the wall, and the jet body clamps through it with a nut and gasket. See How to build the ultimate DIY stock tank hot tub and How to build the ultimate DIY wooden hot tub.

For the Poly Storm gunite jets I use, Waterway makes two body styles. The straight body has a 1in air and 1.5in water spigot, and the tee body takes 1.5in air and 2in water. Decide which one suits your plumbing before you order a box of them.

Are hot tub jets interchangeable?

Only within the same manufacturer and the same jet series. For example, I use Waterway Poly Storm jets on my builds. Poly Storm internals aren’t interchangeable with Power Storm or Poly Jet, even though they look very similar and come from the same manufacturer, because the fittings are different. It goes without saying that you can’t swap in another manufacturer’s jets either. Internals are specific to the housings in your tub.

That’s why I tell everyone: choose one jet system, buy every body and internal from it, and write down the part numbers. In ten years’ time, when you want to replace a cracked internal, you’ll be glad you did. It also keeps your pipe sizes consistent. Don’t mix imperial and metric pipe. There’s more on that in Hot tub pipe: the ultimate guide.

How many jets can I have in my tub?

The number of jets comes down to the pump and the flow. What’s different in a concrete, block or ICF tub is that you tend to have a smaller number of more powerful jets. Plastic shell tubs often market themselves on having dozens, even hundreds, of little jets. That isn’t how our DIY tubs work.

All of the designs in my store are built around 14 or 16 jets. Why? In short, flow.

Working it out

1. Flow per jet. The Poly Storm jets I use need 10 GPM each to work properly. That matches Waterway’s rating.
2. Total flow. 14 jets × 10 GPM = 140 GPM. 16 jets = 160 GPM.
3. Check the pump curve. Every bend, fitting and metre of pipe between the control room and the tub adds resistance, known as total dynamic head (TDH). The more head, the less flow the pump delivers. Look up the flow on the manufacturer’s curve at your system’s head, not the headline number.

Don’t size by the headline figure. The big flow numbers quoted for a pump are the sort you only see with almost no resistance in the system. Once it’s plumbed into a real tub, a pump delivers noticeably less, which is exactly why I allow some headroom. An accurate TDH calculation can be done, but I know that a 3–4HP pump will give enough flow for 14–16 jets in most normal builds, as long as the control room is close and the plumbing is sensible. The full method is in How to correctly size a hot tub pump.

Nozzle size changes everything

Some gunite internals have interchangeable nozzles. For Waterway’s gunite internals, INYO Pools lists about 8 GPM for a 1/4in nozzle, 12 GPM for 3/8in, 15 GPM for 1/2in and 25 GPM for 5/8in. Fit big nozzles all round and 16 jets could need well over double the flow. Check what your internals are rated at before you size the pump.

Want more jets? Add a pump

If you want to increase the number of jets, add a second pump. Just fitting a bigger pump isn’t the best way to do it, and it would only get you a couple of extra jets. If you want around 30 jets, for example, you need a two-pump system, with each pump feeding its own bank of jets. That’s also handy because you can run one bank at a time. There’s more in How many pumps do you need for your DIY hot tub?

Jets (at 10 GPM each)	Flow needed	Typical setup
4–8	40–80 GPM	One smaller jet pump (stock tank, wooden or small tub)
14–16	140–160 GPM	One 3–4HP jet pump, short plumbing runs
Around 30	About 300 GPM	Two jet pumps, each with its own bank of jets

These are planning figures. Your pump curve and pipe sizes decide the final answer. Whatever the jets, the filter and heater run on a separate circulation pump on most of my designs.

Where should the jets go?

The arrangement is totally up to you. There are no real rules about where they go or what clusters you create. A few things to bear in mind:

• Allow for the physical size of the gunite bodies and jet faces. You can’t put them too close together, and you need room for the pipework behind the wall.
• Plan seat by seat. If you want different experiences in each seat, you can. For example, twin rotos at shoulder height in one seat, and directionals low down for the back in another. I placed mine so they hit the middle of my back when I’m sat down.
• Measure for your finished surface. Allow for render, adhesive and tiles so the wall fittings finish flush.
• Keep runs short and balanced. Jets furthest from the pump are the first to feel weak if the manifold is undersized. My DIY hot tub plumbing guide covers pipe sizes and layouts.

What models of DIY hot tub jets are available?

The jets I use on my DIY builds are Waterway Poly Storm. Getting stock of these has always been a bit of a challenge, so it’s worth ordering early rather than waiting until the walls are going up.

I stock directional, roto, twin roto and massage internals, in grey, white and a chrome-look silver finish. Unless someone has a specific requirement, I normally mix and match types around the tub, in the same colour, of course. In the UK, parts4tubs.co.uk sells complete gunite body packs in 4, 14 and 16 jet sets, including a silver jet version. In the USA, parts4tubs.com stocks gunite jet bodies, internals and spares.

Can you use pool parts instead? For returns, yes. For jets, not really. I’ve explained why in Can I use pool parts on a hot tub?

Common mistakes with DIY hot tub jets

• Sizing the pump by horsepower instead of adding up the flow each jet needs.
• Too many jets on one pump. They all end up weak. Two pumps beat one big one.
• Mixing jet series or brands, then finding the internals won’t fit or can’t be replaced.
• Every jet adjustable. If they’re all turned off at once, the pump is deadheaded. Waterway says to always fit at least one non-adjustable internal per spa.
• No check valve on the blower line. Waterway’s instructions say an air check valve is a must if you fit a blower. I’d add a Hartford loop too. See Water in a hot tub air blower.
• Jet bodies set at the wrong depth or not square to the wall, so the fittings don’t sit flush once the tiles are on.
• No pressure test before rendering. Test every jet line before it’s buried.

Troubleshooting weak or odd jets

• All jets weak: check the filter, any closed valves, and whether you have an air lock. See How to deal with a hot tub air lock.
• One jet weak or dead: it’s probably turned off at the face, or something’s stuck in it. Unscrew the internal and check.
• Jets weaker the further they are from the pump: the manifold is too small or the runs are too long.
• Pump is loud and the jets are weak: something may be caught in the impeller. See Noisy hot tub pump?
• Roto won’t spin: scale or debris in the internal. Soak it in a descaler and rinse.

Planning your own build?

My DIY hot tub plans are designed around 14 or 16 jets, with the jet layout, the plumbing and the pump sizing already worked out, plus a full parts list and the video course.

Building a stock tank tub instead? The complete stock tank plumbing kits come in 4, 8 and 16 jet versions. If your design is custom, the Tub & Pool Designer Pro plumbing design service lays out your jets, pumps and pipework for you.

FAQs

How many jets should a DIY hot tub have?

For a block, ICF or concrete tub, 14–16 powerful gunite jets on one jet pump is a good target. If you want more, add a second pump and a second bank of jets.

How much flow does a hot tub jet need?

It depends on the jet. Waterway rates its Poly Storm internals at 10 GPM (about 38 litres a minute) each. Jets with larger nozzles need more, so check the rating for yours.

Can I replace my jets with a different brand?

No. Internals only fit bodies from the same manufacturer and the same series, so match the existing jet exactly.

Do I need a blower for my jets?

No. Jets can run on venturi, drawing air through an open air line. A blower gives a bubblier, stronger feel but needs a check valve and a Hartford loop to keep water out of it.

Why are some of my jets weaker than others?

Usually a jet has been turned down at the face, something’s stuck in it, or the pipe run to it is too long or too small. If they’re all weak, check the filter and look for an air lock.

Got a question about the jets for your own build? 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