Cold Water Systems (Chap 5) Flashcards
How much of Earth’s water is fresh?
Just 3%. The rest is saline
Where is freshwater mostly stored?
In the polar ice caps (69%) and glaciers (30.7%)
What source of freshwater do humans rely on?
Groundwater.
How much UK rainfall is stored?
Just 5%. The rest is finds its way to the water table, rivers and the sea.
Who regulate UK fluid categories?
Water Supply (Water Fittings) Regulations 1999
How many fluid categories are there?
Five
Define fluid category 1
Wholesome water that is clean, cold and potable. Suitable for drinking, domestic use and food production.
Define fluid category 2
Water that is as safe as fluid category 1 but has undergone aesthetic changes: temperature, appearance, taste or odour
Give three examples of fluid category 2 water
– Water heated in a hot water secondary system
– Mixed cat 1 & 2 discharged from combination taps or showers
– Softened water using a salt regeneration process
Define fluid category 3
Water that constitutes a slight health hazard because of the concentration of low-toxicity substances. It is not suitable for drinking.
Give three examples of low-toxicity substances that may be contained in fluid category 3 water
Heating inhibitors such as ethylene glycol (anti-freeze), copper sulphate, chemical additives. Or domestic disinfectants
Give five examples of situations where fluid category 4 water may be found:
- Primary circuits of heating systems
- Water in wash basins, baths and shower trays
- Washing machines and dishwashers
- Hand-held garden hoses with flow-controller sprayers
Define fluid category 4
Constitutes a significant hazard because it contains toxic substances
Give two examples of substances that category 4 water might include
- Chemical, carcinogenic substances (fertilisers/herbicides)
- Environmental organisms
Give three examples of general situations where fluid category 4 water might be present
- Heating system primary circuits in non-single occupancy dwellings
- Fire sprinkler systems (anti-freeze)
- House gardens
- Mini irrigation systems
Define fluid category 5
Water that represents a serious health risk because it contains pathogenic organisms, radioactive material or very toxic substances
Give five examples of situations where fluid category 5 water may be present
- Industrial cisterns and tanks
- Hose union bib taps in non-domestic installation
- Sinks, WC pans, urinals and bidets
- Grey-water recycling systems
- Medical laboratories
- Food processing - butchery, vegetable washing
- Pretty much anything commercial or agricultural
What’s the difference between fluid category 4 and 5?
Risk to health from category 4 would require prolonged exposure (days to months) whereas category 5 could be a short or single exposure
What are the two types of water supply in the UK?
- Supplied by the water undertaker under Section 67 of the Water Act
- Supplied from a private source (borehole, river, stream)
What law regulates water in the UK?
The Water Act 2003 (Water Industry Act 1991)
Which body enforces the Water Act 2003
The Environment Agency
Which body regulates water suppliers and sewerage companies?
Water Services Regulation Authority (Oft)
Which body enforces the obligation of water companies to supply potable water?
Department for Environment, Food and Rural Affairs (Defra)
Which two pieces of legislation relate to plumbers under the Water Act 2003
- The Water Supply (Water Fittings) Regulations 1999
- The Private Water Supplies Regulations 2016
How much water does the average person in the UK use each day?
150 litres
What are the three types of unwholesome water
- Grey water
- Rainwater harvesting
- Black water
What is grey water?
Waste water from baths, showers, washing machines and sinks
How much mains water can be saved using rainwater harvesting typically?
About 50%
Give three examples of uses for harvested rainwater
- Flushing toilets
- Watering gardens
- Supplying washing machines
What is black water?
Water and effluent from WCs and kitchen sinks that can only be treated by a water undertaker at a sewage works
What word is used to describe clean, fresh water?
Wholesome
What are the four treatment stages (in order) to make water wholesome?
- Sedimentation
- Filtration (slow/rapid sand)
- Sterilisation
- Aeration
How do sedimentation tanks work?
They slow the water velocity, allowing solids to sink and settle under gravity
What is turbidity?
The cloudiness or haziness of water caused by particles that are usually invisible to the human eye
What is the purpose of filtration?
It removes turbidity and algae from raw, untreated water
What is the primary purpose of slow sand filters?
To remove microorganisms, algae and turbidity
What size and depth are slow filters typically?
Typically 0.15mm to 0.3mm in size and 0.5 - 1m deep
What’s the biological layer of sludge called?
schmutzdecke – dirt cover
What is floc?
A collection of loosely bound particles or materials bound together by coagulation
What is the primary purpose of rapid sand filters?
To remove floc (but they work for algae, iron, manganese and turbidity too)
What sand coarseness and depth are required for rapid sand filters?
0.5mm to 1mm coarse and 0.6m to 1m deep
Why are pressure filters sometimes neccesary?
They maintain a head pressure so remove the need to pump the water into the supply
What is water sterilised with?
Ammonia and chlorine
What is the purpose of aeration?
To treat groundwater by dissolving metals and gases like CO2
How many reservoirs are there in the UK and who maintains them?
More than 2000 maintained by the Environment Agency
What are the two types of water distribution?
Gravity and pumped
What are the two key industry standards for water maintenance and installation?
BS EN 806 (2011)– Specification for installations inside buildings conveying water for human consumption.
BS EN 8558 – Guide to the design, installation, testing and maintenance of services supplying water for domestic use within buildings and their curtilages.
What is a private water supply?
One that is not provided by a water undertaker and connected to the mains
Which body inspects and tests water quality in private supplies?
Local authorities – as per the Private Water Supplies Regulations 2016
What defines the size of the trunk main?
The population being served. Pipes can be anywhere from 0.2–1.2m in diameter
What size pipe is usually suitable for connecting single dwellings?
25mm
How are non-cast iron trunks connected to households?
A brass strap-type ferrule on PVCu or cementitious asbestos
Explain the two pipes that comprise a water main to a building
- Communication pipe – travels from trunk to boundary. Owned by water undertaker
- Supply pipe – travels to property and owned and maintained by the building owner.
Who maintains the external stop valve?
The water undertaker
What depth must the service pipe run?
Between 750-1350mm
What are the three common options for potable water pipe?
- ‘Blue poly’ – medium density polyethylene pipe (MDPE) @ 25mm
- Softer copper
- 15mm copper in older houses.
What fitting setup is required for internal water meters?
Two stop valves either side and a drain off valve after the meter and before the upper stop tap
What are the four requirements for water entering a property?
- Stop valve located in the building
- Stop valve located above floor level ideally
- Valve located as near to the entry as possible
- Should be a screw down tap/valve
- Must stop water to premises when closed.
What is the maximum MDPE that should be visible?
150mm – it decomposes under UV light
What requirements are there for corrosion of stop taps?
Must be made from gunmetal or corrosion-resistant brass to prevent de-zincification
What markings do copper alloy or gunmetal fittings have?
CR (corrosion resistant) or GM (gunmetal)
