Foul & Surface Water: What's the difference?

November 6, 2015

Here at RPD we're often asked by our customers when carrying drain repairs or emergency pluming what’s the difference between 'foul' and 'surface water'.

To answer this question more thoroughly we’ve decided to dedicate an entire blog post to the subject!

Here’s how it works:

Surface water carries rainwater to local rivers or streams located close to your home. This water is deemed ‘uncontaminated’ since it merely passes through your gutters without passing through your body or being contaminated by chemicals commonly found in your home.

In contrast foul water as the name suggests is considered ‘contaminated’ – either being mixed with human waste or detergents. This water has passed through into your property. When you go to the toilet what comes out the other end is considered ‘foul water’. If you wash your clothes or clean the dishes all water used is likewise considered ‘foul water’. It would be immoral to pump foul water directly into local rivers or streams due to the impact on wildlife. Therefore ‘foul water’ is directed to a sewage processing plant.

When problems occur

Unfortunately DIY plumbing enthusiasts do not understand this distinction. Overzealous plumbing enthusiasts have been known to direct foul water into to the surface water network. In the industry this is known as ‘misconnection’ or ‘cross connection.’ Shockingly Thames Water claims one in ten homes have made this mistake. This has a shocking impact on local wildlife unable to bear the damage this does to their eco-system.

Please remember this fact next time you consider swimming in the local river!

To put this into context Thames Water estimates the equivalent of two Olympic swimming pools of foul water are inadvertently tipped into its region’s rivers every single day!

Most people imagine unscrupulous factories dumping chemicals in to rivers when ask to image water pollution. But the sad truth is normal people like you and me commit the act of water pollution each time the toilet is flushed!

So what is being done to stop this?

The Environment Agency (EA) works with water companies across the United Kingdom in an effort to rectify the matter.

If you live in North West England why not call RPD to inspect your drains. An engineer arrives at your property and inspects each drain outlet. In our experience retro-fit washing machines installed in an outhouse or garage are particularly likely to be subject to misconnection. Saniflo toilets are also vulnerable to misconnection.

If you’re concerned your property could be affected by the above you must act quickly. Under the Environmental Act 1990 you could be fined up to £20,000 for the breach and face criminal prosecution.

Given the lack of intention on homeowner’s behalf prosecutions and fines are in fact rare. The Environment Agency instead issues a warning. If you fail to correct the matter you then become subject to fine and/or prosecution.

If you plan to buy a new property why not take advantage of our home buyers drain survey. Our engineer identifies any misconnections before you buy your new home.


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