Hot Tub Jets Weak or Not Working? A Step-by-Step Troubleshooting Guide

Few things spoil a soak like jets that have gone weak, or a seat where nothing happens at all. In autumn it is a common call: many owners drain and refill before winter, which can leave air trapped in the pipework, and falling leaves and garden debris load up the filters faster than at any other time of year. The good news is that most jet problems come down to something you can check yourself in a few minutes.

Work through the steps below in order. They start with the quickest checks and move on to the ones that take a little longer.

Before you start

Switch the spa off at the isolator, or unplug it, before you take out a filter, remove a jet or open the cabinet. Never run a pump when the water level is low or when no water is moving through it, as this can cause permanent damage to the pump and heater.

Step 1: Check the water level

Water evaporates, splashes out and gets carried out on swimsuits, so the level drops faster than most people expect. If it falls too low, the pump starts drawing in air and the jets weaken or surge. Top it up so the water sits about 25mm (1 inch) above the waterline on the shell, or above the midpoint of the filter housing. Do not overfill.

Step 2: Clean or replace the filter

A clogged filter is the most common cause of weak jets. All the water the pumps move has to pass through the filter first, so when the pleats are packed with debris, flow drops across the whole spa. Autumn leaves make this worse.

• Take the filter out and run the jets for a moment. If they are noticeably stronger without it, the filter is the problem.
• Rinse it with a garden hose, working between the pleats, or soak it overnight in Canadian Spa Filter Cleaner for a deep clean. Let it dry before refitting, as a wet, freshly cleaned cartridge can still restrict flow.
• If it is matted, torn or will not come clean, replace it. Our guide on when to replace a hot tub filter explains the signs and intervals. As a guide, hard-shell and swim spa filters last 6 to 12 months, and portable spa filters 4 to 6 weeks.

Our hot tub filters range lists the right cartridge for each model.

Step 3: Open the jets and air controls

Many jets are adjustable. Turning the outer face of the jet changes the water flow, and it is easy for a jet to be closed off by a bather's back or by someone dialling it down and forgetting. Go round the spa and turn each adjustable jet fully open.

Then check the air controls around the top of the spa. These mix air into the water, so if they are closed, the massage feels gentle even when the water flow is fine. Open them to increase the force.

Our guide to spa jets and controls shows what each jet and control does, using the Toronto SE as an example.

Step 4: Check the diverter

Most spas have a large diverter valve on the topside that moves water between the zones of jets. On a single-pump spa it is normally set in the middle, so the jets flow gently and evenly across all the seats. Turning it fully to one side sends the flow to half the jets, which gives those seats the feel of two-pump pressure while the others go quiet. If some jets feel weak, check whether the diverter has been left turned to the other side, and return it to the middle for even flow. If you're choosing a new spa, our guide to single and twin pump hot tubs explains when a second pump is worth having.

Step 5: Make sure the slice valves are open

Slice valves sit either side of the pump and heater inside the cabinet, and they are sometimes closed for servicing and not reopened. With the power off, remove the access panel and check them. On our spas, a slice valve is open when the handle is pulled out and closed when it is pushed in. A closed valve can restrict flow completely.

Step 6: Clear an airlock

If the jets did not work properly after you drained and refilled the spa, an airlock is the likely cause. This is an air pocket that stops water flowing through the pump. You may hear the pump running but see little or no movement at the jets.

• Turn the jets on and off a few times, switching between low and high speed if your spa has a two-speed pump. This often pushes the air through.
• Do not let a pump run for more than a minute without moving water. If nothing is flowing, switch the power off.
• With the power off, slowly loosen the plumbing union on the suction side of the jet or circulation pump until water flows into the pump and the air has escaped, then tighten it again.

Next time you refill, put the hose directly into the filter housing. Filling this way helps prevent airlocks in the first place. Our guide to filling up your hot tub goes through the full process.

Step 7: Check individual jets for debris or damage

If only one or two jets are weak, something may be lodged inside them. Small debris such as pine needles can get into a jet, which is one reason to site the spa away from overhanging trees. Jets can also work loose, particularly after delivery.

With the power off, remove the affected jet and look for anything caught inside. Many of our jets are removed by turning them anticlockwise, while push-fit jets pull straight out. If a jet is cracked or a diffuser is damaged, you will need the matching replacement. Our guide on which style of jet you have shows how to identify it and lists the part numbers.

When to call an engineer

If you have been through every step and the jets are still weak, or the pump runs without moving water or does not start at all, the problem may be with the pump itself. Do not keep running it. Weak flow can also stop the heater working, as the heater relies on good water flow, so if the water is cooling down too, see our hot tub not heating guide. If the display is showing a code such as FLO, LF or dr, our guide to hot tub display codes explains what it means.

Our hot tub servicing team can diagnose and repair pump faults, or call us on 01293 824094 and we will talk you through it.

Symptom, likely cause and fix

Prevention, so it does not happen again

• Check the water level weekly, and after busy sessions.
• Rinse the filter every two to three weeks and deep clean it at every water change.
• Use a leaf skimmer net in autumn before leaves sink into the footwell.
• Keep the cover on between soaks so debris stays out.
• After draining, refill through the filter housing to reduce the chance of an airlock.
• Leave the diverter in the middle unless you want to focus the flow for a short while.

Replacing a jet

If a jet face is cracked or a nozzle is missing, it is usually a simple swap once you know the type. Note the jet size and style, then compare it with the jets listed in our jets collection or the parts collection for your model in spare parts. Diverter caps and controls are in controllers and valves. If you are unsure which part you need, send us a photo and your model name.

When it needs an engineer

Book a visit if the pump does not start, runs very hot, trips the RCD, leaks from the pump body or makes a grinding noise after you have ruled out low water and an airlock. These usually point to a pump, seal or control fault rather than something you can fix at the shell. Our servicing team can diagnose it, or call 01293 824094. If you are not sure whether a sound is normal, our guide to hot tub noises explains what each one usually means.

Frequently asked questions

Why are my jets weaker after a water change?

Air is often trapped in the pipework after a refill. Running the pumps in short bursts with the filter removed usually clears it.

Can a dirty filter really stop all the jets?

Yes. Everything the pumps move passes through the filter, so a blocked cartridge reduces flow across the whole spa.

Is it normal for some jets to feel stronger than others?

Yes. Jets vary in size and purpose, and some seats are designed for a firmer massage. The diverter and the jet faces let you balance the flow.

Can I run the pump with the filter out to test it?

Only briefly, as a quick test. Put a clean filter back straight away so debris does not reach the pump and heater.

How do I know if the pump itself has failed?

If the pump is silent when selected, hums without moving water after you have cleared any airlock, or trips the power, it needs checking by an engineer.

Quick checklist

• Water level about 25mm above the waterline on the shell.
• Filter clean, dry and within its replacement interval.
• Adjustable jets and air controls open.
• Diverter in the middle for even flow.
• Slice valves open, handles pulled out.
• No airlock after a refill.
• No debris or damage inside individual jets.