Spring is here, and for many UK homeowners, that means one thing: it’s time for the annual patio deep clean. Out comes the pressure washer, ready to blast away a winter’s worth of green algae, moss, and grime from your paving slabs, decking, and garden furniture.
It’s a satisfying job that delivers instant results. But as you connect that powerful machine to your humble garden tap, you could be unknowingly creating a serious risk to the water supply for your entire home, and even your neighbours.
At Plumbers 365, we’re not just about fixing leaks; we’re about preventing problems and ensuring your water is safe. Let’s power through the facts and answer your most important questions about pressure washers and your plumbing.
A pressure washer doesn’t draw water smoothly. Its pump sucks water in bursts. This creates rapid pressure changes in the supply pipe. Plumbers 365 plumbing experts have often seen that the pressure washer pump creates pulsating demand on the water supply, causing the pipe feeding the tap to vibrate against the wall or joist. If the pipe is loosely clipped inside the wall, it vibrates like a guitar string. The noise can sound alarming (like a drill or a machine gun), but it is usually harmless. Securing the pipe with additional clips usually stops it.
Yes. This is a critical and legally required safety measure under the UK’s Water Supply (Water Fittings) Regulations 1999. The regulations state that any “temporary” connection to a tap where the hose outlet could potentially come into contact with contaminated water (like a puddle on a patio, a bucket of car wash soap, or a pond) must be protected by a suitable backflow prevention device. For a garden hose, a Double Check Valve is the standard requirement. Most modern outdoor taps are now sold with one already built-in.
Plumbers 365 plumbing experts often clarify for clients that this is not optional and their water company can prosecute for non-compliance. A garden hose lying on the ground could be submerged in a puddle containing pesticides, dog waste, or fertiliser. Without a check valve, a sudden drop in mains pressure (e.g., a burst main) could suck that contaminated water back into your home’s drinking supply and potentially your neighbours’ supply too.
Backflow is when contaminated water is sucked or pushed backwards into the clean drinking water supply due to a pressure differential. According to drainage experts at Plumbers 365, this is how it can happen:Â
Imagine you’re cleaning your patio and the end of your hose is sitting in a puddle of dirty water containing garden chemicals, pet waste, or other bacteria. If there’s a sudden drop in pressure in your mains water supply (e.g., a water main bursts down the street), it can create a siphon effect. This can literally suck the dirty water from the puddle, up your hose, through your tap, and back into your home’s drinking water pipes. This is a serious public health risk. A check valve physically stops this from ever happening.
Plumbers 365 drainage experts have seen that a domestic pressure washer (100-150 bar) is generally safe for cleaning around drain grates, but the jet should never be aimed directly into a pipe joint. The narrow fan of a consumer pressure washer can force water behind seals on old clay pipe joints or blast the mastic seal off a modern push-fit connection.
If you are cleaning a patio and the jet hits the gap between two drain pipes, you can blow the joint apart underground without knowing. Aim the jet across surfaces, not into gaps.
According to drainage experts at Plumbers 365, this is usually a simple fix. The leak is almost always caused by a perished or missing rubber washer inside the hose connector (the part that screws onto the tap). Unscrew the connector, and you should see a small, black rubber O-ring inside. If it’s cracked, flattened, or gone, simply replace it with a new one from any DIY store. This creates the seal and will stop the leak.Â
According to plumbing experts at Plumbers 365, if your tap is fully on and there’s good pressure from the hose itself, the problem is likely with the pressure washer. The most common causes are:
Plumbers 365 plumbing experts often assure clients that you indeed connect a pressure washer to a kitchen tap, provided you have the right adapter to connect the hosepipe to the kitchen tap’s spout. However, you must still use a backflow prevention device. As your kitchen tap is unlikely to have one built-in, you will need to buy a screw-on double check valve that fits between the tap adapter and the hose connector.
For clients whose old tap doesn’t have a check valve, our plumbing experts advise that they can easily add one. The simplest solution is to buy a screw-on Double Check Valve. This inexpensive brass fitting simply screws onto the outlet thread of your existing tap, and then your hose connector screws onto the other end of the valve. It takes 10 seconds to fit and makes your tap instantly compliant and safe.
Yes. A Temporary Use Ban (TUB) covers pressure washers connected to the mains supply. According to plumbing experts at Plumbers 365, under the Flood and Water Management Act 2010, a hosepipe ban covers “any device attached to a hosepipe.” A pressure washer connected to your garden tap via a hose is explicitly included. Fines can be up to £1,000. However, if you fill a container (e.g., a water butt) before the ban starts and use that, it is generally permitted so check your local water company’s specific rules.
Plumbers 365 drainage experts have often seen that if you store a pressure washer with water inside the pump head, the water can freeze in winter or cause internal corrosion. Properly winterising your pressure washer prevents the pump from cracking in a frost.
Turn off the water supply and disconnect the hose from the machine.
Your pressure washer is a powerful tool, and respecting the plumbing it connects to is vital for the safety of your home’s water supply. A simple, inexpensive check valve is a non-negotiable part of using one safely.
If you’re unsure about your home’s backflow protection or have any other plumbing concerns, the experts at Plumbers 365 are here to help.
Before you start your spring clean, do a quick safety check. If you need advice or help, call Plumbers 365.
