Plumbing In A Washing Machine

Plumbing in a washing machine yourself is nearly always easier than it sounds or looks — and you can invest the money you save in a better machine.

The complicated part of this job is deciding where to put the machine in relation to the available plumbing fittings. This can be made easier by approaching it in a logical order. The actual plumbing work is usually simplicity itself thanks to the wide range of special fittings for the do-it-yourselfer that have come on to the market in the last few years.

Siting the machine

It isn’t only the space you have available which dictates where you put your washing machine. Just as important — more so in many cases — is the ease with which you can connect it to the supply pipes, your drainage system, and a power supply.

Consider these problems one by one, bearing in mind what ways of doing the job you feel happiest about and also any local authority restrictions that are in force in your area.

Plumbing in a washing machineThe supply pipes

All washing machines need a cold water supply, and many take a hot water supply too, so it follows that the ideal site is close to the relevant water pipes — however you decide to break into them.

Many people like their machine to go near the sink or in a washroom with exposed pipework: not only does this give easy access to the supplies, it also puts the outlet within reach of a drainage point. But don’t let the proximity of water pipes influence you too much. It’s far better to let the most convenient drainage point dictate the site and then extend the supply pipe routes to fit in with this. What you must en-sure is that where you choose to break into the pipes gives you enough room to do the job properly.

Telling hot pipes from cold is easy — unless you have central heating. You must ensure that your hot feed is connected to the pipe supplying a hot tap — not a heating pipe. If there’s likely to be any confusion, turn the heating off and run the hot taps.

Then mark the pipes at the break-in site so that you don’t muddle them up later.

On indirect plumbing systems with a cold storage tank, the cold water pipe you’ve selected might be the rising main or the branch of it that runs direct to the kitchen sink cold tap. In this case, a word of warning: some local authorities do not permit home owners to interfere with the rising main, in which case you must find a supply fed from the tank. Check this point before you proceed any further with the project.

Water pressure: On direct water systems, this is governed by the rising main pressure; there should be no problem but your water authority can supply details if required. On indirect plumbing systems the pressure is governed by the head — the distance between the base of the storage tank and the washing machine inlets. Normally the minimum head required is 2.44m (8ft). If yours isn’t, consult a plumber about ways of boosting the pressure.


Of all the site considerations, this is invariably the overriding one. The reason is simple — you have to fit in with your existing drainage system, or else face a prohibitive amount of work.

However you connect the drain outlet on your machine to the waste system, it should meet the relevant water authority regulations.

These are designed to guard against the possibility of back- siphonage — dirty water being sucked back into the machine, with the risk of contaminating the supply. There are two ways to arrange this.

The easiest is to use a special fitting which taps into the waste pipe from a sink or another appliance. The fitting has a valve in it to ensure that the flow is one way — that is, to rule out the chance of back-siphonage into the machine. A variation on this theme is the washing machine trap, which includes an extra waste inlet and replaces the existing trap underneath, say, a sink.

The alternative method is to connect the machine outlet via a standpipe and trap (to avoid the siphonage problem) to its own waste pipe. This can then be tied into the waste pipe of another appliance or — with more difficulty — entirely separately to the nearest available waste outlet.

The main drawback to the first method is that the washing machine must be near an existing waste pipe for it to be practicable. A second point is that not all washing machine manufacturers endorse it, and not all authorities permit it. However, it is the easiest so it’s worth checking up on before you go any further.

The difficulty with the second method nearly always centres around one of two things: either there is no convenient waste to tap, or the drain outlet is untappable. But if you have to run a separate waste you must also bear in mind that it should run in as straight a line as possible, at a gentle downward gradient, otherwise it will be illegal. For details, see above.

Your choice of suitable outlets depends on the type of drainage system fitted for your property. In a two pipe system you can connect into a gully or a waste stack. The gully option is usually simple, and so is the stack if the washing machine is at first floor level because you can generally run it into a hopper head.

Connecting directly to the stack is difficult, and unless there’s a spare inlet hole on it, it’s not really worth considering for the sake of a washing machine — select an alternative site where drainage poses less of a problem for you to deal with.

Modern single stack systems impose even more restrictions. There are fewer gullies and it’s often much harder to break into the stack. Weighed against this however, waste systems from existing fittings and appliances are generally more straightforward — so you should be able to find an easier option than connection to the drains direct.

As with supply pipes, there are various local authority restrictions relating to drainage — some, for example, are very particular about the way you connect a new waste pipe to a gully.

Fortunately, water authorities with tight restrictions are usually very helpful when it comes to offering practical advice. So contact your inspector and tell him what you propose to do — after all, the rules are there for a reason and you may save yourself from a costly mistake.

Electricity supply

Of all the services, this offers the most flexibility. If you can’t run the machine’s flex, via a plug, to a nearby outlet, you have the choice of adding a new socket or — better, because it gives the machine its own supply — a fused connection unit. But you must have electrical experience before you attempt these projects. Bear in mind though that in Britain if you want to put the machine in the bathroom, the supply point must either be outside the room or else be an approved fused connection unit with pull cord switch.


Australian and New Zealand laws prohibit do-it-yourselfers from doing most plumbing and electrical work.

What you need

When you have decided on a site, familiarize yourself with the different techniques and materials for breaking into the supply pipes and drainage system.

What you eventually buy will depend on the nature of your existing plumbing, the access on and around the site, and what you feel is the easiest way of doing the job. Often this is a matter of personal taste. Many of the special accessories listed below would be too expensive to use on large-scale plumbing jobs, but on a small project like this they pay for themselves 10 times over.

Start by looking at plumbing-in kits, which are now becoming more widely available. Some deal only with the water supply, some with the drainage and others with both. Getting everything in one go certainly makes life easier but it is only worth it if the parts provided actually suit your site. Check this before you buy; all kits will contain a combination of the fittings described below.

Water supply: On each pipe, you need a tee connector, a stop valve, a washing machine connector to match the inlet hose on your washing machine, and enough pipe or flexible connectors to piece the new run together. These, however, are the basic requirements: they can often be simplified by using one or more special accessories.

Automatic connectors break into supply pipes without you having to turn off the water supply, eliminating the need for tee branches. Unfortunately, very few of the many types on the market are actually approved by washing machine manufacturers and water authori-ties (most let the cut-out section of pipe fall into the supply when you first connect them, which can damage the machine).

One type that is safe is simply clamped around the pipe at the break-in point. Striking a pin on the fitting then activates a small charge which sends a cutter across the side of the pipe and automatically retains any metal cuttings in the fitting itself.

Washing machine connectors generally combine a connection point with a stop valve in the same fitting. As you must always fit stop valves, this saves a lot of trouble.

As well as accessories, you need to decide what new pipework and jointing system to use. As regards the pipe, you have the choice between copper and plastic. If you opt for plastic, you can buy special adapters for connecting to an existing run of copper.

Where necessary, though, check that the plastic pipe is suitable for both hot and cold water. Pipe size for both materials is 15mm.

When it comes to joints, the choice is generally between compression and push-fit. Both are much more expensive than the soldered type, but they are far easier to fit too. And as you don’t need many anyway, it’s the simplicity that should tip the balance. Do check, however, that any accessories you are buying are compatible with both the pipe-work and the jointing system.

When you cannot connect a washing machine connector/stop valve direct to the supply pipe, it’s a good idea to sketch a plan of the new pipe run. Mark in approximate pipe lengths and the points at which you need joints or flexible connectors. List all the items

before visiting your plumbing supplier. Drainage: Again, there’s plenty of choice. But in this case what you eventually need will be determined by your break-in method. Itself determined by the site.

Automatic connectors for breaking into existing plastic waste pipes are very useful and have more general approval because the section cut out when you make the connec-tion is discharged straight into the drain. You simply clamp the fitting onto the waste pipe —most designs have a sleeve so that they can be used with any size of pipe. Then you make a hole in the pipe using the cutter provided, and screw on the valve nozzle — which connects to the washing machine’s outlet hose.

Washing machine traps offer an alternative easy connection method. You simply trim the new trap to match the existing pipework, fit it in place of the original waste trap, then slip the machine outlet hose over the nozzle.

Standpipe kits contain all you need if you want to do the job the other way. But in this case you’ll also need elbows, tees and straight sections of new waste pipework to connect to the existing waste, to a.gully or to the stack. The waste pipework should be 38mm UPVC: if your existing waste pipe is 32mm, be sure to get the right adapter joint. Miscellaneous: Under this section come all the other bits and pieces needed to complete the job. Work out a comprehensive list once you’ve finalized the connection method.

Compression joints on supply pipes need jointing compound or PTFE tape, as do screw-on waste pipe and trap connections. Waste pipes are normally solvent jointed, for which you need the proper cement. If you add exten-sions of any length, you need wall brackets.

If you run a waste pipe through a wall, make sure you have the tools to make the hole and the materials — sand and cement, mastic, plaster — to patch it afterwards. If the pipe connects to a gully, it should do so below the grid — buy a new plastic grid so that you can cut the appropriate holes.


Once you’ve established your break-in point, the most daunting part of connecting the new supply pipe(s) is severing the existing ones. Yet it really is very easy: do the job methodically and there’s little that can go wrong.

Start by draining down the pipes concerned; cut off their water supply, then open the taps at the ends of the runs to empty them.

The rising main (and all the cold pipes in a direct plumbing system) can be isolated by closing the main stop valve — unless, that is, you’re lucky enough to find a local stop valve just before the break-in point.

In indirect systems, cold pipes other than the rising main are isolated by closing the valve on the main feed at the base of the storage tank. If there is no such valve, tie up the ball valve and turn on the taps to drain the tank.

In the absence of local valves, the supply to a hot pipe is effectively cut off by closing the valve on the cold feed to the hot water cylinder or heater. But in this case, be sure to turn off any heating systems first.

Note that if you decide to use automatic connectors there is no need either to cut off the supply or to drain down.

Draining down won’t remove all the water in the pipes, so put a bowl or some rags underneath the break-in point to catch drips.

Breaking in: The procedure given here is for a standard compression-jointed tee connector.

Start by marking the length of the fitting against the pipe to be cut. Don’t forget to allow for the fact that the pipe ends fit into it by 20mm on each side.

Now cut the pipe at the first mark using a junior hacksaw. As you do so. Make absolutely certain that the cut is square or the joint will be ruined.

Support the cut ends as best you can, then cut through the pipe at the second mark in exactly the same way. Follow by filing off the burred metal around the pipe ends: use a flat file for the outside edge and a round file on the inside.

Connect the tee to the pipe run as shown in Joining pipes.

Automatic connector: The instructions here are for a Thorsman T- plus. First make sure that the connector is the appropriate size’ for the pipe. Then clamp it over the break-in point using the Allen key provided.

Connect the rest of the new pipe run to the branch on the fitting and make sure the stop valve you have fitted is in the closed position — this is vital: the supply pipe still has water in it, so activate the cutter on the fitting before the branch is closed and you’ll have a flood on your hands.

To pierce the supply pipe, remove the plastic cover on the strike pin. Support the pipe run with pieces of wood, then hit the pin hard with a hammer. The charge inside the fitting will cut the hole. And the branch will be supplied with water.

Connecting the run

How you do this depends on how far the supply has to go and what fittings you use. If you are running hot and cold pipes, keep them together.

Plug in power supply or install fused connection unit The conventional sequence after the tee is: section of pipe/stop valve/section of pipe/ washing machine connector. All these can be compression-jointed as described overleaf. Make absolutely certain, though, that you cut the ends of the pipe sections square or leaks are bound to occur. Secure the new runs where possible using plastic pipe clips pinned to the wall. A washing machine connector with built-in stop valve simplifies the run and is fitted in the same way.

Extending the run: This is easily done, if necessary, using straight sections of pipe in conjunction with elbow fittings and bendable connectors. Follow the rules below to avoid problems.

Keep hot and cold pipes running together, about 25mm apart.

Choose a route that is unobtrusive — dlong the skirting or in the angle between wall and ceiling are two favourites.

On no account let the run contain any sharp kinks or inverted U bends that could restrict the flow or create airlocks later.

Secure straight runs of pipe every 1m using plastic clips.

Proper planning will usually avoid the need to run pipe through a wall. If it is necessary hire a drill and follow the method described for the waste pipe.


If you are lucky, this is simple. But even adding a new waste pipe is not the daunting task it first appears.

If you are breaking into an existing waste pipe with an automatic connector, start by clamping the special fitting over the break-in point; tighten the four screws securely. Next, using the special tool provided with the fitting, bore a hole in the waste pipe through the hose outlet nozzle. Finally, screw the nozzle/valve assembly into the fitting until hand-tight.

Washing machine trap: Measure this for size against the existing trap. Mark off on the new trap where it has to be cut.

To ensure a square cut, wrap a piece of cardboard around the trap inlet

and align it with the mark. Level it up all round, then use it as a template while you cut the pipe with a junior hacksaw.

Place a bowl under the old trap to catch the water in it. Unscrew the trap inlet and outlet joints, remove the old trap and fit the new one in its place. Wrap a few turns of PTFE tape around the joint threads to guard against leaks. Finally, screw on the hose outlet nozzle (note that this has no valve — the sink over-flow will prevent siphonage).

New waste pipe: In this case you must have a standpipe. The standpipe should end at least 600mm above floor level; secure it to the wall behind where the washing machine is to go using the clips provided.

Plan the run of the new waste. The 38mm waste pipe can be solvent, compression or push-fit jointed. Clip it to the wall every 1m or so.

Waste pipe branch: Do this job with the 38mm tee fitting of your choice. Sever the existing pipe with a junior hacksaw, having measured and marked on it the exact size of the fitting. Use a cardboard template to keep the cuts square.


There are many different ways to join two sections of pipe. The only ones which are important here are compression and push-fit for water pipe, and push-fit and solvent-welded for plastic drainage pipe.

Whatever sort of joint you use. Make sure that the pipe is cut accurately square and to length. Remove any burrs left by, the cutting.

Always ensure that the diameter of the joint matches that of the pipe. This may not be immediately obvious. In the case of the water pipes, there should be no problem only 15mm pipe is concerned. And with compression and push-fit joints, you can even connect to the older Imperial ‘/2in. Pipe (which you may well have) without an adapter.

The waste pipes may not be so simple. There are two standard sizes: 38mm and 32mm. But even within the same size. Differ-ent makers’ pipes are not neces-sarily interchangeable. It may well be essential to use the same brand for the extension.

Compression joints

Remove the capnut from the joint and slip it onto the pipe. The seal is made by the small ring under the capnut — called an olive.

Slip this over the end of the pipe. If you are fitting to plastic pipe. You also need a metal insert to stiffen the end.

Push the end of the pipe into the joint until it butts firmly igai mist the end of the recess. Wnip a little PTFE tape around the threads of the joint then screw up the capnut finger-tight, making sure that the pipe doesn’t pull out of place.

Now grip the body of the fitting with a spanner or adjustable wrench, and place another on the nut. Tighten it to compress the olive — but restrict this to one or two turns at most to avoid damage. Some makers provide specific instructions on this point — follow them.

For a better seal — particu-larly when joining to Imperial pipes — apply pipe jointing com-pound to the mating surfaces of the joint and pipe.

Push-fit joints

Push-fit joints for water pipe are somewhat similar to compres- sion joints — except that the seal is made by a rubber ring and you can do the nut up by hand. As well as the seal. There is an additional metal grab-ring which stops the pipe pulling out.

Stiffen plastic pipe with a metal insert. With either plastic or copper, smear a little silicone lubricant on the end and insert it through the seal and grab-ring. Tighten the capnut firmly by hand.

Some waste pipe joints are similar — although no insert or grab- ring is used. With others, there is no capnut and the end of the pipe is simply pushed firmly into place. It is important that these joints are not strained.

Solvent-weld joints

Unlike the other joints described, these are permanent — so you must get them right first time. Dry assemble first and mark both joint and pipe so you can align them properly.

Clean the mating areas thoroughly — there is a proper cleaner but meths is adequate. Then spread solvent cement on the mating area of the end of the pipe, aiming for a thin, even coating.

Immediately push the pipe home in the joint and hold it in correct alignment for 15 seconds.

Gully connection: In this case the pipe will probably have to pass through an outside wall. On a masonry wall, mark the site of the hole and drill a pilot hole from inside using a masonry bit.

Convert this into a hole just larger than the pipe diameter using a hammer and a long cold chisel. Or, alternatively, hire a heavy duty masonry bit or core drill from your local store and do the job with this.

Run the new pipe to the gully in the most convenient and straightforward way secure it at metre intervals.

When you reach the gully, replace the existing grid with your new plastic one, cut to accommodate the pipe. The pipe should terminate at least 50mm below the grid line.

Make good the gaps in the wall around the pipe — with mortar on the outside, filler or plaster on the inside — but leave a gap of about 2mm all around the pipe. Caulk this afterwards with non- setting mastic — inside and out — so that the pipe can expand and contract without stress.


Always follow the manufacturer’s instructions_ on this point. The washing machine hoses simply screw on to the rele-vant connectors: red for hot, blue for cold. The drain hose can be slid onto the outlet nozzle or simply slipped into the top of the standpipe (don’t fasten it), depending on your drainage connection, One final point that people often

forget about or don’t do properly is that the machine must be level, or the balance of the drum could be upset. Check this with a spirit level after you have connected up and slid the machine into its final position.

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