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How to use a Bosch pressure washer

Updated: 21.10.2026

The paper guide in a new Aquatak is thin, and the first afternoon is where the motor either throws a steady jet or gets blamed for a fault. You are connecting a corded Bosch to an outside tap, or wondering whether a water butt will do. This page, from the Products Compared editorial team, is how to use a Bosch pressure washer for that first start. The sequence is the one in the AdvancedAquatak 140 manual. Follow the manual in your carton if a step differs. It is not a ranking of the seven listings in our [Bosch pressure washer comparison](/hub/compressors/bosch-pressure-washer). A qualifying purchase can earn us a commission at no extra cost to you.

The paper guide in a new Aquatak is thin, and the first afternoon is where the motor either throws a steady jet or gets blamed for a fault.

Our top picks

Bosch Bosch Fontus 18V-6 (no battery)

Best overall

Bosch Bosch Fontus 18V-6 (no battery)
6.2/10about £131.58
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Bosch Bosch EasyAquatak 120

Best value

Bosch Bosch EasyAquatak 120
8.3/10about £89.95
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Bosch Bosch UniversalAquatak 135

Rank 3

Bosch Bosch UniversalAquatak 135
8.6/10about £108.00
View offer
On this page
  1. 1.What you need before you switch on
  2. 2.The start sequence
  3. 3.When the motor stops on purpose
  4. 4.A water butt is a different set-up
  5. 5.Stop and get help

What you need before you switch on

You need a UK outdoor socket with RCD protection and a water supply the pump can drink. If the lead is cut, crushed or taped, stop. A trigger gun is not backflow protection. The Water Supply (Water Fittings) Regulations 1999, Schedule 2 paragraph 15, match the device to the fluid category. The Advanced manual, written for 230 V and class I, forbids use on the drinking supply without a backflow valve. A domestic hose-union double check is only fluid category 3. Higher-risk connections are a question for the water undertaker.

The start sequence

Attach the supply hose, open the tap, and bleed the gun with the motor off until the stream is steady. Then fit the nozzle, point the lance at the ground, and plug into the RCD-protected socket. A fan jet is the right first nozzle. A pencil or rotary jet is the wrong first choice on soft stone. Eye protection and staying off ladders are part of the Electrical Safety First advice. If the next job is slabs, distance and nozzle limits are on the Bosch pressure washer for a patio page.
Bosch Bosch Fontus 18V-6 (no battery)

Testsieger

Bosch Bosch Fontus 18V-6 (no battery)
6.2/10about £131.58
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When the motor stops on purpose

The motor stopping as you let go of the trigger is autostop. The Advanced manual has the pump rest when the trigger is released and restart when you squeeze. If you never bled the gun, or the tap is closed, self-priming is meant to stop after about 25 seconds. A leak at a connector is a common note on the UniversalAquatak 135. Tighten the joint you can see. Do not open the pump. Which model to buy is on the best Bosch pressure washer page.

A water butt is a different set-up

Bosch’s self-priming kit, part F 016 800 421, is a separate accessory around £34: a 3 m hose, a strainer and a non-return valve. The Advanced manual’s lift with that kit is about 0.5 m. Do not drop a garden hose into a butt and hope. Corded tank-volume fields on amazon.co.uk are not tanks. The Fontus 18V-6 is the model in this set with a real 6 litre tank, and it is a different tool.

Stop and get help

Stop if you feel a tingle, if the RCD will not reset, or if the lead is wet and damaged. Stop if a jet has punctured skin. Injection injuries need urgent care even when the cut looks small. Stop if the pump has already run dry past the priming limit. The Consumer Rights Act 2015 gives 30 days to reject faulty goods when a machine will not prime on a sound tap after a proper bleed.

Common questions

What do I connect first, water or mains?
Connect the supply hose and bleed a steady stream with the motor off, then plug in. The AdvancedAquatak 140 manual is the source of that order, and your carton manual wins if it differs. The high-pressure hose is already in the box. The hose from the tap is a separate reinforced line of at least 12.7 mm. Power before water leaves the pump running on air.
Why does the motor stop when I release the trigger?
That is autostop. The pump rests when the trigger is released and restarts when you squeeze. If pressure does not return, check that the tap is open and that you bled the gun first. If the pump has been trying to prime for about 25 seconds with no water, stop and fix the supply. Do not keep restarting a dry machine.
Can I run it from a water butt?
Only with Bosch’s separate self-priming kit, part F 016 800 421, around £34, with a 3 m hose, a strainer and a non-return valve. The Advanced manual’s lift with the kit is about 0.5 m, and priming should stop after about 25 seconds if water has not arrived. The hose in the washer carton is not that kit. A butt outlet below the lift is the wrong set-up.
Do I need an RCD?
Yes for outdoor use. Electrical Safety First expects a UK 3-pin plug and an RCD, and these listings do not print a BS 1363 claim you can rely on instead. Use a socket that already has RCD protection. A trip that will not reset is an electrician’s visit, not a reason to try another socket in the rain.
Can I use it in the rain?
No. Electrical Safety First says not to use a pressure washer in the rain and not to spray sockets. A damp patio with a dry plug is a different situation from working in a downpour. If the lead is wet, stop and dry it before the next use. A taped repair on a wet lead is not a fix.
What diameter of garden hose does Bosch specify?
The AdvancedAquatak 140 manual specifies a reinforced supply hose of at least 12.7 mm from the tap to the inlet. That is not the high-pressure hose in the carton. A thin, kinked hose starves the pump and makes autostop feel like a fault. Fit the inlet filter. A trigger gun is not a backflow valve on the drinking supply.

Related pages

Bosch pressure washer buying guide

Bosch pressure washer

Best Bosch pressure washer for each stated home job

EasyAquatak vs UniversalAquatak: the flow and hose

Bosch pressure washer for a patio: nozzle and stone

Sources

Public UK sources and the Bosch DIY pages below. amazon.co.uk listings checked on 19 October 2026. Listing prices, stars and review counts are those shelf figures.

  1. Bosch DIY UK: pressure washers (retrieved 19 October 2026)
  2. Bosch DIY: AdvancedAquatak 140 manual (11 MPa rated, 230 V, class I) (retrieved 19 October 2026)
  3. Bosch DIY UK: Fontus 18V-6 (retrieved 19 October 2026)
  4. Bosch DIY UK: guarantee (retrieved 19 October 2026)
  5. Electrical Safety First: pressure washers (retrieved 19 October 2026)
  6. Water Supply (Water Fittings) Regulations 1999, Schedule 2 paragraph 15 (retrieved 19 October 2026)
  7. GOV.UK: noise nuisances, how councils deal with complaints (retrieved 19 October 2026)
  8. Consumer Rights Act 2015, section 22 (retrieved 19 October 2026)