WRAS has developed a number of videos providing information relating to the Water Supply (Water Fittings) Regulations 1999, the Water Supply (Water Fittings) (Scotland) Byelaws 2014 and the Water Supply (Water Fittings) Regulations (Northern Ireland) 2009.

How the plumbing regulations affect you

The water industry has investigated a number of incidents where water from toilet cisterns 
has been siphoned back into customers' plumbing systems.

The likely cause of this problem is the way in which the two components found in cisterns
(water inlet valve and flushing valve) are installed.

To help customers and installers, we have created the following video which illustrates how
this can happen and it shows how you can check your own toilet cistern to see if you might
have the same problem. 

How should a toilet cistern be set up?

Ensuring the components are correctly installed will prevent the water in the toilet cistern 
being siphoned into the drinking water supply.


How to check the air gap
The protective air gap in toilet cisterns is the vertical measurement between the overflow
level and the CL level mark. (The overflow level must always be below the CL level but
above the water line marked on the cistern).

The actual size of air gap will depend on the size of pipework and inlet valve supplying the 
cistern. Most toilets have a 15mm connection which must be protected by an air gap of at
least 3cm (30mm), but for those with a 20mm  (3/4") connection, the minimum air gap
would be at least 4cm (40mm).

What to look for
Here is a refresher of what you should be looking for, click on the type you have and check 
how it should be set up.

If you have doubts as to whether your toilet might have a problem, get an Approved Plumber
to check.

Approved Plumbers
There are a number of Approved Contractors' Schemes which are run by water companies
and trade associations in the UK.

The Approved Contractors' Schemes run by the trade associations are authorised by the
Secretary of State under the Water Fittings Regulations and Scottish Byelaws.

The WaterSafe installers' Scheme is a partnership between the seven Approved Contractors' Schemes in the UK. It provides a free to access online register and search facility of approved plumbing contractors working in the UK and it helps promote Approved plumbing businesses.  Click here to search for an Approved Plumber.
Below is a list of the schemes which operate across the UK.


Anglian Water (A Plus) - Parts of the east of England 

Severn Trent Water (WaterMark) - Parts of the Midlands, North Wales and West of England

Thames Water (TAPS) - Parts of London and the Thames River area

Water Industry Approved Plumbers' Scheme (WIAPS) - Areas of England and Wales 
not covered by the above companies.

Association of Plumbing and Heating Contractors (APHC) - Across England and Wales

Chartered Institute Of Plumbing and Heating Engineering (CIPHE) - Across
England and Wales.