Don’t misconnect your washing machine or dishwasher to the plumbing

connect appliances right to prevent environmental damage If your washing machine or dishwasher is connected to the wrong water drainage system it is misconnected and you are contributing to damaging the local environment. Harmful chemicals in detergents and other waste products can pollute local rivers and streams.

The water being pumped out of these appliances can also contribute to flash flooding by overloading the rainwater drainage system. Is yours? Read this article to find out more.

What’s the problem?

Save-the-earth If someone connects any part of our plumbing incorrectly we could be part of an environmental problem. It’s also illegal. You may be completely unaware of plumbing “misconnections” unless you check (there are instructions on how to check later).


It could have happened before you moved in but it’s the current householder who is responsible for putting the plumbing right. It shouldn’t be too difficult to put right in most cases.

Here’s how a misconnection can happen

There are two distinctly different drainage systems available to most households.

One is for waste water from toilets, sinks, washing machines and dishwashers to discharge into. This water ultimately gets treated.

The other is situated at the bottom of the fall pipes from our guttering for rainwater. This water runs untreated into rivers.

They have different jobs, they are totally separate systems, and must not be mixed up.

Unfortunately, many thousands of houses do have these systems mixed up. This is called a misconnection.

Why does it matter?

Your washing machine or dishwasher could be pumping waste water containing harmful chemicals into local rivers. Or it could be contributing to overloading the storm drains in heavy rain making flash flooding more likely.


I myself have been a victim of this. This article describes my experience, which should be helpful in showing you exactly what to avoid – or how check your existing connections.

My personal experience

I moved into a new house and connected my washing machine up to the existing plumbing which was in the garage.

The previous occupier had installed a washing machine in the garage to leave space for a dishwasher in the kitchen, but had misconnected it to the storm drains instead of the sewerage system for waste water. See below for details and photos.

Washing machine misconnected to storm drain

The following 2 pictures show my garage with brown-coloured guttering and fall pipes round the back.


At the bottom of the fall pipe is a grate. Rainwater from the garage roof’s guttering runs into this grate and goes into the storm drain. This harmless rainwater joins the surface water drainage system under our roads and runs untreated directly into local rivers and streams.

Unfortunately, you can also see a grey pipe to the left. This is the waste water pipe that the washing machine pumps out into.

This washing machine is misconnected! Its waste water full of harmful chemicals and bleaching agents is being pumped into the storm drain designed only for rainwater. It is ending up in a local river. This needs correcting.

Out-buildings and garages

Out-buildings and garages aren’t normally connected to the sewerage system. This means most people installing a washing machine are likely to misconnect the waste water pipe to the storm drain instead – which is illegal.


How to make sure you have no misconnections

1: Look at the large 4 inch stack pipe on the outside of your home where the toilet is connected (see photo below).

2: No fall pipe from the guttering should be connected to it. If it is, heavy rain will overload the sewerage system.

3: Look at the guttering and fall pipes on your house and other out buildings.

4: No other pipes from sinks or appliances should connect to this system. Only rainwater should run into it.

5: At the bottom of the guttering fall pipe there may be an open grate. Only rainwater from the roof should run into this grate or be connected to this fall pipe. No plumbing from an appliance or sink should be connected in such a way that it runs into this pipe or grate.


(Pic 3)

This picture (Pic 3) shows a 4 inch main waste water pipe which is typically found at some point on a house. The waste water pipes from the bathroom, kitchen and appliances such as washing machines and dishwashers should all be connected to this pipe or pump out into a grate next to it.

(Pic 4)

This photo (Pic 4) shows a sink waste pipe running into a grate which is right next to the main 4 inch water water pipe. The dishwasher in the kitchen also pumps out through this pipe. This connection should be OK as the grate is connected to the sewerage system underground.

(Pic 5)

This photo (Pic 5) shows everything connected correctly.


On pic 5 you can see that the lone pipe on the side of the house runs round the corner and connects to the main 4 inch pipe. This is correct. The lone pipe actually passes underneath the fall pipe for the guttering. Someone could potentially have taken the easy option and connected the lone pipe to the fall pipe at the corner. This would have resulted in soap, dirty water, shampoo and other undesirable liquids draining into the local river or stream.

More on misconnections

I have more information on plumbing misconnections including official diagrams, a video and other photos of good and bad real life cases.


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16 thoughts on “Don’t misconnect your washing machine or dishwasher to the plumbing”

  1. My husband and I relocated our Washing Machine into our garage 3 years ago. We spent time, energy and money to make sure that we plumbed it correctly. You are so right, it is tempting to plumb it to the nearest, most convenient drain. But, we resisted and did the right thing. I am very glad I did, I would worry about the environmental effects each time I used it, which would have ‘drained’ me more than the extra time and effort during the installation! Great article!

    However, I have since had a related problem. My Washing Machine works perfectly well most of the year, but every winter since it has been in the garage it becomes temperamental. It does not function well when the temperature is below 5 degrees (or there abouts). I wish to purchase a new machine, but I don’t know which models/makes work well in the cold (of a drafty garage). Any advice? Any recommendations?

  2. Thank you for your comment Joey. I would guess the vast majority of people are unaware of this problem. I certainly was. At least if people know about it they can make an informed choice about whether to do it properly or not.

    Garage’s are not ideal places for appliances although because of a very small kitchen I am forced to keep my freezer, tumble dryer and washing machine in my garage. As far as I know all washing machines sold in the UK are the same as far as temperature goes. They are all designed to be installed in kitchens or utility rooms. The main problem I would envisage is if the temperature falls below freezing where it could freeze water in the fill valves and hoses. I have seen flooding caused by a cracked water valve. I would not expect issues at around 5° although maybe the electronics don’t like it.

    Another possible source of your problem could be condensation forming on the electronics. It is possible and other washing machine might perform better worse more the same it all depends on how it is designed. The only thing that could suggest is to buy good quality one but as I say I am not aware of any specifically designed to cope with conditions in a garage. Good ventilation may also help.

  3. What has failed to be mentioned is the fact that thousands of households generally built in the earlier half of the 20th century, have combined rainwater and sewage drainage, ie one pipe for all, waste can be connected to these type of systems.

    1. Yes, this article caused me to panic thinking I had some expensive remedial work to do, then I read than most houses built prior to 1950s/1960s have only a “combined sewer” that takes both surface water and foul water. So panic over.

      I’m now trying to irrigate the garden with the washing machine greywater, so the lack of a lateral drain shouldn’t be such a moral issue, but a few washing machine modifications might be called for….

      1. Clearly if theres only one drainage system you have no choice but to connect everything to it. The issue is about when there are separate systems for rain water and waste water.

  4. If there is no other drain except say a surface water drain in a garage running to a soakaway, is there a box of some sort that can treat the washing machine water for dumping into the surface water drain?

    This may be a more cost effective way – if available of course.

  5. There are separate washing machine tanks that pump the water to a foul water drain. Do any have small pipes like 22mm, as some SaniLavs have? Then a small pipe can run under the floorboards or whatever to the nearest foul drain in the house.

  6. i live in a 100 year old terraced house and i want to connect a rain water pipe from the gutter into to my soil pipe is this ok as i think all the waste water runs in to the main sewage system.

    many thanks

  7. Hello Chris: It isn’t as bad as connecting the output of a sink or washing machine/dishwasher to the storm drain but it is still a misconnection. This is because the extra water running into the soil pipe system during heavy rain can overload the waste water network and can result in the flooding of land and/or properties.

    Whether this actually happens in any particular area would presumably depend on how many people have connected pipes meant for the storm drains to the soil pipe. I can’t help thinking if it was just the water from one gutter it might not be too bad, after all the water is clean, but of course if enough people do it there will be a lot of extra water running into the soil pipe network during heavy rain which could potentially overload it.

  8. Hi
    My daughter has recently purchased a washing machine on moving to a flat. The store where she purchased it from arranged for the delivery person to connect it to existing pipework as past of the deal. However, although is seems to be correctly fitted to this pipework, when she empties her kitchen sink, some of the waste water is running into her washing machine. Is it possible to fit some sort of one way valve to the washing machine waste pipe to stop this?

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