Unit 315 Session 6 Backflow protection in plumbing systems

​BACKFLOW PROTECTION IN PLUMBING SYSTEMS

​The Water Supply (Water Fittings)

Regulations have been put in place to ensure that the plumbing systems we install and maintain prevent:

● contamination of water

● wastage of water

● misuse of water

● undue consumption of water

● erroneous metering of water.

Of these, by far the biggest issues surround

contamination.

Open Ended

What ways do you think mains water can become contaminated

​Up until 1999, there were three classes of fluid.
At that time, water was either considered wholesome, suspicious or dangerous.
With the implementation of the 1999 Water Regulations, these three fluid categories became five to bring the UK into line with the rest of Europe.

​Fluid categories

​Fluid category 1

Fluid category 1 is wholesome water supplied by a water undertaker, complying with the Water Quality Regulations made under Section 67 of the Water Industry Act 1991.

​Fluid category 2

Fluid category 2 is water that would normally be

classified as fluid category 1 but whose aesthetic

quality has been impaired because of:

● a change in temperature

● a change in appearance, taste or odour owing to the presence of substances or organisms.

These changes are aesthetic only and do not constitute

a health risk.

​Fluid category 3

Fluid category 3 is water that constitutes a slight health hazard because of the concentration of low toxicity substances. Fluids in this category are not suitable for drinking or any other domestic purpose or application.

​Fluid category 4

Fluid category 4 is water that constitutes a significant health hazard because of the concentration of toxic substances, which can include:

● chemical, carcinogenic substances or pesticides

(including insecticides and herbicides)

● environmental organisms of potential health

significance.

​Fluid category 5

Fluid category 5 represents a serious health risk

because of the concentration of pathogenic organisms,

radioactive material or very toxic substances. These

include water that contains:

● faecal material or any other human waste

● butchery or any other animal waste

● pathogens from any source.

Open Ended

Research and give at least 3 examples of situations where you may find fluid category 2 water

Open Ended

Research and give give 3 examples of situations where you may find fluid category 3 water

Open Ended

Research and give give 3 examples of situations where you may find fluid category 4 water

Open Ended

Research and give give 3 examples of situations where you may find fluid category 5 water

Match

Match the following descriptions to the correct fluid category

• These changes are aesthetic only and do not constitute

  a health risk. Typical situations where this may occur in

  domestic properties are:

  ● water heated in a hot water secondary system

  ● mixed fluid categories 1 and 2 water discharged

  from combination taps or showers

• Typical situations are:

  ● in houses, apartments and other domestic dwellings:

  ● water in the primary circuits of heating systems

  whether chemicals have been administered or

  not

  ● water in washbasins, baths and shower trays

  ● clothes and dishwashing machines

  ● home dialysis machines

• Typical situations are:

  ● fire sprinkler systems using anti-freeze

  chemicals

  ● house gardens:

  ● mini irrigation systems without fertiliser or

  insecticides, including pop-up sprinkler systems

  and permeable hoses :

  ● commercial dishwashers

  ● refrigerating equipment

• Typical situations are:

  ● industrial cisterns and tanks

  ● hose union bib taps in a non-domestic installation

  ● sink, WC pans, urinals and bidets

  ● permeable pipes in any non-domestic garden

  whether laid at or below ground level

  ● grey water recycling systems

Fluid category 2

Fluid category 3

Fluid category 4

Fluid category 5

• Fluid category 2

• Fluid category 3

• Fluid category 4

• Fluid category 5

​Backflow and back siphonage

​Back flow – caused when a downstream pressure is greater than the upstream or supply

pressure in the water undertakers main or the

consumer’s potable water supply. Back pressure can be caused by:

● a sudden loss of upstream pressure, such as a

burst pipe on a water undertaker’s mains supply

● an increase in downstream pressure caused by

pumps or expansion of hot water

● a combination of both of the above.

​Back siphonage – backflow caused by a negative pressure creating a vacuum or partial vacuum in the water undertaker’s mains cold water supply. It is similar to drinking through a straw. If a sudden loss of pressure on the mains supply was to occur whilst a submerged outlet was flowing, then water would backflow upwards through the submerged outlet and down into the water undertaker’s main.

​Whole site, zone and point of use protection

​Whole site protection

The term ‘whole site protection’ simply means that the water undertaker’s main is protected at all times from backflow or back siphonage from any fluid category that is not fluid category 1 by a suitable backflow device. Protection should be at the point of entry of the cold water supply.

​Zoned protection

Zoned backflow protection simply means that where different fluid categories exist within the same building, premises or complex, these have their own backflow

protection devices to protect any part of the system that is fluid category 1.
Zoned protection is also

required where any water supply pipe is supplying more than one separately occupied premises.

​Point of use protection

This is the simplest form of backflow protection. Point of use backflow protection devices are used to protect an individual fitting or outlet against backflow and are usually located close to the fitting which they protect, such as a single check valve on a mixer tap to protect against fluid category 2 or a double check valve on a domestic hose union bib-tap as protection against fluid category 3.

​Research project

​You are to use appropriate sources to produce a word document giving a brief description accompanied with an image of the following 7 types of non-mechanical backflow protection.