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AirJet vs HydroJet: bubbles or water jets?

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In short

AirJet systems blow air through holes in a floor ring to make a wall of bubbles, which feels gentle and fizzy. HydroJet systems use a pump to push water through nozzles in the wall, which gives a firmer, directed flow. HydroJet tubs usually keep an air ring too, but they cost more, weigh more and have an extra pump to maintain.

Details as stated in the Amazon listing or by the manufacturer. See the current price on Amazon.

Our verdict

Pick the Lay-Z-Spa Milan AirJet Plus for a lighter, simpler tub with plenty of bubbles. Pick the Lay-Z-Spa Hawaii HydroJet Pro if you want water jets as well and a square shape for a patio corner.

Jets are what most people picture when they think of a hot tub, but inflatable tubs use two quite different systems. Most have an air blower that pushes air through a ring of small holes in the floor. Some, such as Lay-Z-Spa's HydroJet Pro models and several semi-rigid tubs, add water jets in the walls, driven by a pump. This guide explains how each works, what they feel like, how they affect water temperature and noise, and whether the step up to water jets is worth it.

How AirJet bubbles work

An AirJet system uses a blower in the pump unit to push air through a channel in the floor of the tub. The air escapes through dozens or hundreds of small holes, which is why listings quote jet counts of 100 or more. The bubbles rise around your body and give a light, fizzy feel rather than a focused massage.

Air blowers are simple and reliable, and the system has no extra plumbing in the walls. The downside is that the air comes from outside, so on a cold day it carries some heat out of the water. Many tubs limit how long the bubbles can run in one go; the manual gives the limit for your model.

AirJet

Air from the blower, up through holes in the floor ring.

HydroJet

Water from the pump, out through nozzles in the wall.

AirJets blow air through holes in the floor; HydroJets push water through nozzles in the wall.

How HydroJet water jets work

A HydroJet system uses a water pump to draw water from the tub and push it back out through nozzles in the wall. Each nozzle often mixes in some air for a stronger stream. Because the flow is directed, you can sit with a jet aimed at your back or feet, which feels quite different from bubbles.

There are far fewer water jets than air holes. The Bestway Santorini listing gives 10 jets, while the MSpa Denver lists 8 swivel hydro jets plus 130 air jets. HydroJet tubs usually keep an air ring too, so you can choose bubbles, water jets or both.

Two Lay-Z-Spa models compared

These two Lay-Z-Spa tubs from our guides show the difference within one brand.

FactLay-Z-Spa Milan AirJet PlusLay-Z-Spa Hawaii HydroJet Pro
Jet systemAirJet PlusHydroJet and AirJet
Jets listed140148 in total
Seats66
Water916 L795 L
ShapeRound, 196 cmSquare, 180 cm
WallTritechTritech
Weight empty38 kg54.3 kg
AirJet and HydroJet Lay-Z-Spa listing facts

See premium tubs with water jets →

Heat loss, noise and power

Do bubbles cool the water? Air drawn from outside is colder than the water in most UK weather, so long bubble sessions take some heat out. On a 13 A supply, some tubs also pause the heater while the blower runs, because both share the same socket. Water jets move water that is already warm, so they cool it less, though some heat is still lost at the surface.

Both systems make noise. Air blowers tend to have a loud whoosh, while water pumps hum. Neither is silent, so consider neighbours if the tub sits near a fence.

Note:Check the manual for how long jets may run and whether the heater works at the same time. Keep the pump unit dry and plugged into an RCD protected outdoor socket.

Upkeep and reliability

An AirJet system has fewer parts to go wrong. A HydroJet system adds a pump, pipework and nozzles, which can collect biofilm if water care slips. Regular purging with a suitable line cleaner, following the chemical maker's instructions, and keeping filters clean help. HydroJet pumps also add weight: the Hawaii is over 16 kg heavier than the Milan according to the listings.

Which should you choose?

If you are unsure, an AirJet tub with a good cover is the safer first buy. Our best inflatable hot tubs guide covers both kinds.

  • Choose AirJet if you want a simple, lighter tub for relaxing in bubbles and easy upkeep.
  • Choose HydroJet if you want directed jets and are happy with more weight and a dearer tub.
  • Choose a tub with both if different people in the household prefer different feels.

Frequently asked questions

Is HydroJet worth it? If you want water jets you can aim, yes. If you mainly want warm water and bubbles, AirJet is simpler.

Do bubbles make a hot tub colder? Long sessions can, because outside air passes through the water. Keep the cover on between uses.

Can I run the heater and jets together? It depends on the model. Some 13 A tubs pause the heater when the blower runs; check the manual.

Why do AirJet tubs list so many jets? Each small air hole counts as a jet, so numbers run into the hundreds. Water jets are counted per nozzle.

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