HOW TO: PLUMBING IN A DISHWASHER

INTRODUCTION

Plumb a washing machine or dishwasher into your kitchen or utility area.

You will need an electrical socket close by. If there is no socket you need to consult the B&Q leaflet

“Fitting extra electrical sockets” or call a qualified electrician.

 

SKILL LEVEL

Plumbing fittings require simple mechanical skills. Elementary knowledge of your plumbing system

will help you locate the valves to turn off the water. You also need to know where the existing drainage runs to.

SAFETY FIRST

Check walls for the position of pipes and cables before drilling. Make sure the dishwasher is earthed and

that all metal pipes are earthed. Wear eye protection when using a drill, hammer or chisel. Positively

identify pipes by feeling them while you run various taps - you should detect the hot getting hotter and

the cold getting colder.

TO COMPLETE THIS PROJECT YOU WILL NEED...

• Copper Pipe (15mm)

• Filling Knife

• Hose (Jubilee) Clip (25mm)

• Junior Hacksaw

• Masonry Bit

• Open-Ended Adjustable Spanners

• Pipe Clips (32mm)

• Power Drill (corded)

• Screwdriver

• Screws

• Spirit Level

• Tape Measure

• Wall Plugs

• Washing Machine Trap

• Washing Machine Valves (Lever Type)

• Waste Pipe (40mm)

• Waste Pipe Fittings

• Wood Bit

 

1- OVERVIEW

The basic job of plumbing in a washing machine is identical to a dishwasher except that most washing

machines use hot and cold water and dishwashers run from a single (usually cold water) supply with one hose.

The most complicated part of the plumbing is not getting the water in but getting it out to the drain. Supply

pipes can be run vertically as well as horizontally to avoid obstructions. Waste pipes, however, must fall away

to the drain, so you need to plan this aspect before you begin.

2- PLANNING

Take a good look at the possible positions for plumbing in the machine. Changing your mind halfway through

installation can be avoided with careful planning, so try to work through it in your mind as you read this guide

 to see if any unexpected snags come to light, and draw out a plan on paper before starting work.
If at all possible, avoid hacking up floors to run waste pipes.

The easiest position to plumb in a machine is directly next to a sink because the supply and waste pipes are

already in place.

Most manufacturers recommend that the hot and cold valves are turned off at the completion of every wash

because a hose could burst and cause a flood. In practice, many people never remember to do this but it is

still necessary to have the valves in an accessible place, such as under the sink cupboard, in case you

should need to turn them off quickly.

Read the machine instructions fully before starting work, in case there are any do’s and don’ts that you

need to be aware of.

 

3- SLOW FILLING

If the cold-water tank supplying your hot cylinder is only a metre or so above the height of your machine, the
low pressure could cause problems with the hot fill. It is sometimes possible to change the solenoid valve in
the machine, but an easier way is to join both hoses to a ‘Y’ piece and run the machine from the cold only.

The immersion heater in the machine will heat the water but it takes longer to complete some cycles.
If the machine is in a fairly remote position in the house, it could be worth connecting both hoses to cold fill only.

This is simply because the hot fill will use the dormant water in the hot pipe (which is cold) and have to heat it up

anyway, so all you will be doing is drawing more hot water into the pipe to go cold.

4- FLOODING OVER

If you live in a flat, you need to be extra careful that the machine won’t flood over and pour into the property

below. This can happen if the waste pipe blocks and the water rises up over the top. If there is any risk of

this, you should use a sealed connection to the stand pipe with an air inlet valve, or plumb the waste into a

washing machine trap.

5- HIGH-PRESSURE NOISES

Many people experience knocking in the pipes when the machine’s integral solenoid valves shut off.

The mains water is stopped abruptly and this can cause shock waves along the pipe. The easiest answer

is to slow the flow to the machine down by closing the supply valve slightly. Also make sure the new

pipework is properly clipped and not loose.

6- WASTEPIPE OPTIONS

The machine waste pipe needs to be at

least 40mm (1.5in) in diameter. The flexible hose from the machine must discharge into the waste pipe above the level of the top of the drum. If the flexible hose is lower, it will cause the machine to empty by siphonic
action. To avoid this, you will also need an air break where the flexible hose joins the waste pipe to stop it siphoning.

 

The simplest way to join a hose to a waste
pipe is through a washing machine trap.
This allows the waste water to back up
slightly into the sink instead of flooding
over the floor. Cut the spigot end off and
push the flexible hose onto the pipe. Use
a jubilee clip to secure it. The air gap is
provided through the plug hole or overflow
pipe to the sink.

Make sure the flexible hose is held up above the level of the sink overflow so

water from the sink doesn’t flow into the washing machine      1

Use a piece of string or vine tie to keep the hose high.

If there isn’t a convenient sink nearby, the waste can be taken out through a hole in the wall via a washing-machine standpipe to a drain .

Make sure the drain connects with a foul-water sewer and not with a rainwater soakaway. If you are unsure, ask your local authority for help in identifying the correct drain.

Use an electric drill, a cold chisel and a lump hammer to make a neat, round hole in the brickwork. Push a length of 40mm (1.5in) plastic waste pipe through the wall. Make sure it runs slightly down to the outside.

An access tee on the outside (instead of an elbow) will help you to clear blockages in the waste pipe that

might occur .

7- JOINING PUSH-FIT WASTE PIPES

Cut the pipe end square and chamfer it with a file or abrasive paper so it pushes past the rubber seal in the

fitting. Smear a little silicone grease on the pipe end before pushing it in. Pull it back out of the fitting 2mm

to allow for expansion when hot water passes through.

8- JOINING SOLVENT-WELD WASTEPIPES

Cut the pipe end square and remove any rough edges with fine abrasive paper. Wipe the pipe end very

lightly with the abrasive paper to remove any grease. Apply a thin film of solvent cement to the pipe end

and push it in to the fitting.

The solvent cement will set almost instantly, so be sure the fitting is in the correct position.

 

9- JOINING SUPPLY PIPES

The easiest way to join pipes is by using

push-fit or compression joints 4

Cut the pipe end square and remove burrs
with a file. Alternatively, use a pipe-cutting
tool which gives the perfect edge for
pushing into fittings.

 

10- COMPRESSION JOINTS

Assemble the nut and ring on the pipe end
and screw the nut hand tight 5

Then use a spanner to tighten the nut a
further turn. If you want to make certain
that the fitting won’t leak, smear jointing
compound around the brass ring before

reassembling the joint and tightening. There is no need to wrap the threads with PTFE.

Use a slip-tee washing machine valve to join to an existing pipe.

11- FITTING A VALVE

Turn off the water at the stopvalve and drain out any residue through the lowest tap. Cut the pipe with a

junior hacksaw. Remove 15mm of pipe, unless the pipe will slide up slightly to give you enough room to put

the fitting on. If the pipe is fixed firmly at both ends, you can pull one side slightly away from the wall and

push on a slip tee which slides up the pipe and then back down again to the branch position. Mark the final

position with a pencil so you can place the tee over the gap.

If the valve needs to be in another position for ease of access, use a tee and a length of pipe, then place

the valve on the end of the pipe.

Make sure there is a rubber washer in either end of the flexible hoses and

attach to the valves and the machine. You shouldn’t need to use a wrench. If the nut won’t seal, try fitting an extra rubber washer in the hose end.

12- PUSH-FIT JOINTS

Push the pipe firmly into the fitting and then pull back to make sure the grab

ring is holding the pipe     6.

13- SELF-CUTTING TAPS

If you don’t want to go to the trouble of cutting pipes and turning off the water, you can use self-cutting taps to make connections to the supply pipe and
self-cutting outlet clamps to the waste pipe. Place the clamp around the pipe and bolt it firmly on. Then wind in the self-tapping mechanism. This pierces the pipe and allows water through.

The major drawback of these fittings is that some machines will show a fault and lock out because the filling

or drainage rate is too slow. Check with the manufacturer’s instructions to see if this type of arrangement is

suitable. These type of valves can only be fitted to 15mm copper pipe and not pipes made from other materials.