Drain Jetting Guide

Drain jetting is vitally important to the safe and effective delivery of drainage services. This Catalyst Services UK guide is designed to give service users an overview of drain jetting, helping them to better understand what to expect from drainage contractors.

What is drain jetting?

Drain jetting, also known as sewer jetting, is the process of pumping water under pressure into drain and sewer pipes to clean them and remove blockages. In effect, a jet of water – hence the term water jetting – is used to break up unwanted material.

The material can then be removed from the pipe, leaving it clear. Or, because it has been broken up, it will be carried along the pipe by the wastewater in it.

How is drain jetting done?

Drain jetting is carried out by connecting a powerful water pump to a flexible hose with a nozzle at the end of it. The hose is guided into the drain pipe. The pump is them switched on to force water through the hose and out of the nozzle into the pipe.

The power of the water jet is determined by the pressure the water is under and the volume of water flowing out of the nozzle, referred to as a water flow rate.

For standard water jetting, pressures can rise to 4,000 pounds per square inch (psi) or 275 bar, with no limit on flow rate.

However, to remove very tough material from drains and sewers – for example concrete – water pressures of up to and over 12,000 psi (827 bar) can be used. Drain jetting at such high pressures is very specialised and can only be carried out by very skilled operatives (See: Can drain jetting damage my drains?).

What is drain jetting used for?

Drain jetting has three main purposes:

To clean drain and sewer pipes so they remain in good working order. This is an important part of planned drainage maintenance, preventing problems before they can occur, and ensuring a property’s drain and sewer system works well all the time.
To remove material that builds up inside pipes, causing drain and sewer blockages. This is a reactive drain jetting service. Drain blockages can occur if planned maintenance is not carried out, or if there is a sudden event, for example a storm, that results in blockage material entering the drain or sewer.
Drain jetting is often needed as part of other drainage maintenance and refurbishment tasks. For example, drain jetting is carried out to ensure CCTV drainage survey cameras can be sent along pipes to check their condition. It is also carried out before drain pipes are rehabilitated by the installation of liners.

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Why is drain jetting important?

Drain jetting is essential to maintain drain and sewer systems properly. Most pipes in drainage systems are buried underground. Even drain pipes in buildings are hard to reach.

Drain jetting is a remote access method for keeping them clean and free from blockages. If a drain or sewer pipe becomes blocked, the only alternative may be to excavate it and remove the blocked section.

This would cause significant disruption, take much longer for blockages to be cleared, and would be much more costly than drain jetting.

Root infestation

Being underground, drains and sewers can become filled with tree and shrub roots. This process is called root infestation. It happens when very small roots grow through pipe cracks and displaced pipe joints, then multiply and expand inside pipes. A common method for removing these root infestations is by drain jetting.

FOG, wipes, and detergents

Drain jetting has become increasingly important because drainage systems are used more intensively, especially in towns and cities.

Also modern lifestyle choices increase the risk of blockages. For example, large volumes of fats, oils and grease – known as FOG – are wrongly disposed of down sinks.

Residues from washing powders, detergents, shampoos, and soaps (gels and bars) can also build up in pipes, reducing their diameters and, eventually, blocking them. Also, items such as wet wipes and sanitary products are wrongly flushed down toilets. Both of these behaviours greatly increase the risk of blockages, which require them to be drain jetted.

What kinds of drain jetting are there?

Types of drain jetting are defined largely by the size of the pumps and hose systems used – and also by the types of nozzles attached to hoses.

Drain jetting with van packs

Most drain blockages are cleared using drain jetting equipment installed in a van – known as a van pack. This contains a pump, a water tank, a reel of hose, and a selection of jetting nozzles.

Different nozzles can be selected, depending on the design and condition of the pipe, and the cleaning or blockage removal task that needs to be undertaken (See: Drain jetting nozzles, below).

The van also usually carries CCTV drainage survey cameras.

Drain jetting with jet vac tankers

To remove bigger blockages and to clean pipes over longer lengths and with larger diameters, a more powerful drainage vehicle, called a jet vac tanker, may be needed.

These HGVs have larger pumps and wider diameter hoses to allow them to deliver water jets with higher flow rates. This increases the force of the water jets, which means they can:

Clear larger volumes of material.
Tackle harder and more compacted material.
Clear waste that is less granular, for example stones and rocks.
Operate in larger-diameter and longer pipes, including culverts.

Jet vac tankers can also suck up blockage material with vacuumation equipment, reducing the chance of further blockages, and minimising pollution risks.

The most powerful jet vac tankers are used to remove large blockages, including fatbergs. Fatbergs contain FOG and other items, usually wet wipes, and can block long lengths of sewer pipe.

Drain jetting nozzles

Jetting nozzles play a crucial role in the drain jetting process. The design of the nozzle determines the type of jet created and its pressure. In simple terms, for a given amount of water pumped through the hose, the smaller hole in the jetting nozzle, the higher the pressure.

So, a fine nozzle (such as a pin jet, see below) will generate a high pressure (low flow rate) drain jet needed to remove concrete from a pipe. But a plough jet with a high flow rate (but lower water pressure) is used to remove large volumes of silt from a pipe.

Rear and forward facing nozzles.
Rear facing only nozzles.
Fan jet nozzles that apply a wide-angled jet of water for drain cleaning.
Spinning (or rotating) nozzles – that deliver a water jet over a larger area and help agitate and break up blockage material.
Pin jet nozzles – that deliver very fine, higher pressure water jets.
Flail jet nozzles – that combine water jets with spinning chains for tackling hardened blockages
Plough jets – designed to flush silt, mud or stones out of pipes.
Bomb jet nozzles – for clearing heavily contaminated or blocked pipes.

Is drain jetting safe?

Drain jetting is safe if it is done properly. The main risk is caused by the pressure and flow rate of the water jets. Water under pressures as low as 100 psi (7 bar) can penetrate human skin.

At higher pressures, these injuries, called fluid injection injuries, can be catastrophic, even fatal. They can be caused by an operative losing control of the hose and the water jet hitting their body, or by a hose bursting, releasing an unexpected jet of water.

Research commissioned by the Water Jetting Association found a second serious risk was an uncontrolled hose striking an operative’s head or body, causing a major trauma injury.

Therefore, it is very important that drain jetting is done by people using the right equipment, including specialist personal protective equipment (PPE), plus the right training, qualifications and experience.

Drain jetting is carried out from access points into pipes. These can be manholes, gullies, rodding eyes, or excavations. This creates slip, trip and fall hazards. In some cases, safety procedures must be used that are similar to those used when working at height. Working on drains and sewers also presents significant hygiene risks.

Can I do drain jetting myself?

Drain jetting is a specialist process and should not be attempted by householders or business owners. Trying to carry out drain jetting with equipment not designed for the task is very unlikely to clear blockages or clean drain pipes. In fact, it is more likely to make blockages worse or create new blockage problems.

Who should carry out drain jetting?

Drain jetting should only be carried out by drain cleaning and unblocking contractors who have the right skills, qualifications, experience and equipment to carry out the task safely and to a high standard.

What qualifications do drain jetters need?

The most widely used training courses for drain jetting are provided by the Water Jetting Association, the member body for the UK water jetting industry. Its water jetting courses are accredited by City & Guilds.

For drainage engineers to hold a WJA water jetting card and certificate, they must pass a one-day WJA Safety Awareness course and then at least one of four one-day WJA practical modules, usually selecting the one for drain and sewer jetting.

The National Association of Drainage Contractors also provides a one-day high pressure water jetting training course, certified by EU Skills, which covers all aspects of the safe use of high pressure water jetting units.

Are there recognised standards for drain jetting?

The WJA has a Code of Practice for the safe use and working of water jetting equipment in drains and sewers, known as the Red Code. This is recognised by the Health and Safety Executive as setting the approved standard for drain jetting in the UK. It is also used by drainage contractors and regulatory agencies in many other countries to guide the use of drain jetting equipment.

Can drain jetting damage my pipes?

Drain jetting equipment is very powerful. If it is not used properly, it can damage drain and sewer pipes, especially if they have already been weakened by being damaged or displaced.

Pipes have maximum water pressure allowances depending on the material they are made from – for example, clay, plastic and metal. A jetting nozzle left static in one place in the pipe for a period of time can also cause damage to the pipework.

Drainage engineers use their skill, experience and set procedures to ensure the drain jetting they carry out does not damage pipes in this way.

What are the alternatives to drain jetting?

There are five common ways to clean or unblock drain pipes and sewers if drain jetting is not to be used.

Chemical cleaning. ‘Clog-busting’ chemicals can be bought that usually claim to clear blockages quickly and easily. These contain powerful acids that dissolve some residues that build up in pipes. However, these chemical products do not work every time. They will not be effective against larger blockages and many items that may be blocking drains, such as plastics, metals, silts, stones, and vegetation. Also, they introduce chemicals into drains that are a pollution risk.

Drain rodding. This is a common method for removing pipe blockages that are close to drain entry points. Flexible rods can be screwed together and pushed along drain pipes towards the location of the blockage.

The drain rod has a plunger cup on the end that can be moved backwards and forwards, creating a vacuum pressure that, in most cases, dislodges blockages and allows the material to be flushed through the pipe.

The risk with drain rodding is that the rods, themselves can become stuck in pipes, creating an even worse blockage problem.

Electro-mechanical pipe cleaning. A mechanical device powered by an electric motor can be used to clean the inside of pipes and remove blockages. It has a cutting head on a long, flexible cable stored on a reel. The cable is fed into the pipe so the cutting head can be used to scour the sides of the pipe or cut through a blockage at a specific point.

This method is commonly used to clean drainage systems inside large buildings and in wastewater downpipes where using drain jetting risks water escaping through lateral connections, causing internal flooding.

Mechanical pipe cutters. If there is a very tough blockage at a specific location – for example concrete in a pipe, or a metal stake that has been driven through a pipe – a remote access mechanical cutter can be sent along the pipe to remove it. Despite their names, most of these machines have powerful grinding heads, not cutters, that an operative can used to break up the blockage, guided by a mini video camera.

Pipe excavation. If the remote access ‘no dig’ options described above are not appropriate, the only other option is to excavate the pipe. Then the pipe can be broken into and the blockage removed. Usually, the pipe is then repaired by replacing the entire section of pipe affected by the blockage.

Is drain jetting environmentally-friendly?

Yes it is. Because drain jetting is a remote access method to maintain pipes, it uses less effort and energy than is needed to carry out an excavation.

Because drain jetting is such a powerful process, blockages can be removed relatively quickly, so only a relatively small volume of water is used. Also, no chemicals are added to the jetting water.

Jet vac tankers can suck up blockage material, removing substances like FOG that are a pollution risk and could cause further blockages. Also, some jet vac tankers, called recyclers, can filter and reuse this water, reducing the amount of water needed to carry out drain jetting.

What happens to blockage material after drain jetting?

All material sucked up by jet vac tankers, or taken out of drains by van pack drainage engineers, during drain jetting is taken to an authorised waste site for safe and legal disposal.

Where blockage material is not removed during drain jetting, it eventually reaches a sewage treatment works where sophisticated equipment is used to remove it as part of the water cleaning process.