Don’t misconnect your washing machine or dishwasher to the plumbing
There are two separate drainage systems under most UK streets: one for waste water (toilets, sinks, appliances) which is treated; one for rainwater which runs untreated into rivers. Connecting appliance waste water to the rainwater system is a misconnection. Garages and outbuildings are particularly at risk because they are rarely connected to the sewerage system – making a misconnection easy to make accidentally.
If the waste water pipe from a washing machine or dishwasher is connected to the rainwater drainage system rather than the sewerage system, harmful detergent chemicals drain untreated into local rivers and streams. This is called a plumbing misconnection. It is illegal and it may have happened before you moved in – which does not change the current householder’s responsibility to correct it.
The Two Drainage Systems
Most UK properties are served by two entirely separate underground drainage systems that must never be connected to each other.
Sewerage system (foul water drain)
Receives waste water from toilets, baths, sinks, washing machines, and dishwashers. This water is pumped to a treatment works where harmful substances are removed before the treated water is discharged. The external pipe serving this system is typically a large 4-inch stack pipe on the outside wall of the property.
Surface water drain (storm drain)
Receives only rainwater from roof guttering and external surfaces. This water runs untreated directly into local rivers and streams. It connects to grates at the base of fall pipes from the guttering. No waste water from appliances, sinks, or toilets should ever enter this system.
Why Misconnections Are Common
Misconnections often happen because the two drainage systems look similar from the outside and their connections can be physically close together. The problem is particularly common in garages and outbuildings, which are rarely connected to the sewerage system. Anyone installing a washing machine in a garage and connecting the drain hose to the nearest available pipe or grate risks connecting to the rainwater drain rather than the foul water system.
Outbuildings and garages are almost never connected to the sewerage system. Any grate or pipe in a garage floor or at the base of guttering fall pipes goes to the surface water drain. Connecting a washing machine waste pipe to any drainage point in a garage without verifying it connects to the foul water system is likely to result in a misconnection. See our guide on putting a washing machine in a garage for what to check before installing.
How to Check for a Misconnection
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Locate the main 4-inch waste stack pipe on the outside of the property.
This is usually a large plastic pipe (typically white or grey) running vertically down an outside wall close to the bathroom or kitchen. All waste water from the property should ultimately connect to this pipe or to an approved grate directly beside it.
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Check that no guttering fall pipes connect to the waste stack.
Rainwater from roof guttering must not discharge into the foul water system. If any fall pipe from the roof guttering connects to the main stack pipe, this is a misconnection in the other direction – rainwater overloading the sewerage system.
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Trace the waste pipe from the washing machine or dishwasher.
Follow the drain hose or waste pipe from the appliance to where it exits the property. Confirm it connects to the main foul water stack pipe or to a grate that is itself connected to that system – not to a grate at the base of a guttering fall pipe.
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Check grates near guttering fall pipes.
A grate at the base of a fall pipe receives rainwater from the roof. No appliance or sink pipe should connect to or discharge into this grate. If there is any appliance pipe near a guttering fall pipe grate, verify they are separate systems before assuming the connection is correct.
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If in doubt, consult a plumber or the local water authority.
The local water authority may be able to advise or inspect drainage connections. A qualified plumber can trace the drainage routes and confirm whether any misconnection exists.
Consequences of a Misconnection
Environmental pollution
Waste water from washing machines and dishwashers contains detergents, bleaching agents, fabric softener, and other chemicals. When this water enters the surface water drain, it flows untreated directly into local rivers and streams, polluting the water and harming aquatic life.
Flash flooding risk
Appliance waste water discharged into the surface water system during heavy rain adds to the volume of water the storm drains must handle. Combined with heavy rainfall, this can contribute to surface water flooding in local streets.
Legal responsibility
A plumbing misconnection is illegal regardless of when it occurred or who made it. The current householder is legally responsible for ensuring drainage connections are correct. A misconnection discovered when selling a property may require correction before completion.
Installation Guides
Related Guides
How to Connect an Appliance ProperlyCorrect drainage connections for washing machines and dishwashers – with diagrams and photos.
Washing Machine in a GarageWhy garages are particularly at risk of misconnection – and what to check before installing.
How to Install a Drain HoseCorrect drain hose installation – height, routing, and connection to the waste system.
How to Install a Washing MachineFull installation guide including water supply, drainage, and levelling.
Frequently Asked Questions
How do I know if my washing machine is misconnected?
Trace the waste pipe from the machine to where it connects to the drainage system. It should connect to the main foul water stack pipe (the large 4-inch pipe on the outside wall near the bathroom or kitchen) or to a grate that connects to that system underground. If it connects to a grate at the base of guttering fall pipes, or to any drain that receives rainwater, it is misconnected.
What happens if I have a misconnection?
Detergent chemicals and other waste from the appliance drain untreated into local rivers and streams via the surface water system. During heavy rain, the extra water volume can contribute to flash flooding. A misconnection is also illegal – the current householder is responsible for correcting it regardless of when it was made or by whom.
Can I put a washing machine in a garage and drain it correctly?
Yes, but it requires connecting the waste pipe to the foul water system – which garages typically are not connected to. A new run of waste pipe to the foul water stack, or a specialist pump system, is usually needed. Do not connect to any existing grate in the garage floor or at the base of guttering – these are almost certainly surface water drains. See our full guide on washing machines in garages before installing.
16 Comments
Grouped into 10 comment threads.
2 replies 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 reply I live in my own property a business man has put a dish washer in next door but it upstairs he has put the waste water pipe onto the rain water collection pipe when it rains and they have the dishwasher on my front garden gets flooded as the drain is in my part of the front garden is this OK
I live in my own property a business man has put a dish washer in next door but it upstairs he has put the waste water pipe onto the rain water collection pipe when it rains and they have the dishwasher on my front garden gets flooded as the drain is in my part of the front garden is this OK
Hello Gillian. If a dishwasher or washing machine is pumping out its dirty water full of detergent into a drain that is connected to the gutters to channel away rainwater then it is misconnected. As my articles explain, misconnections contribute to flash floods, and can pump harmful chemicals into local rivers, which is why the misconnections campaign was set up in the first place.
1 reply Hi While doing my elderly mothers garden last weekend I noticed her neighbours who have a large brick built utility building at the bottom of the garden have put what I think may be the outlet hose from the washing machine into my mother's garden hanging over the fence. I moved it to the other side of the fence but have concerns regarding this as this half of my mother's garden (several feet) has been saturated to the point where we thought it may be dangerous to walk on the grass as you would sink into a hole for the last couple of years. Can you confirm if from a legal and environment point of view are they allowed to do this (if this is the case) and also are there any health implications ?personally I am disgusted if this is what they are doing but I haven't actually seen water coming out of the pipe but will be looking out for it over the coming weeks and will try and record this on my phone. Also who would be the best people to report this to Severn Trent or Public Health?
Hi While doing my elderly mothers garden last weekend I noticed her neighbours who have a large brick built utility building at the bottom of the garden have put what I think may be the outlet hose from the washing machine into my mother’s garden hanging over the fence. I moved it to the other side of the fence but have concerns regarding this as this half of my mother’s garden (several feet) has been saturated to the point where we thought it may be dangerous to walk on the grass as you would sink into a hole for the last couple of years. Can you confirm if from a legal and environment point of view are they allowed to do this (if this is the case) and also are there any health implications ?personally I am disgusted if this is what they are doing but I haven’t actually seen water coming out of the pipe but will be looking out for it over the coming weeks and will try and record this on my phone. Also who would be the best people to report this to Severn Trent or Public Health?
1 reply 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
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
Likely replying to chris wood
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.
1 reply 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.
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.
0 replies Rob: Read this Washing machine fills with water overnight or when switched off
0 replies 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?
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?
0 replies 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.
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.
0 replies 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.
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.
0 replies 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?
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?
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.
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….
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.