4 Pipework Installations in Domestic Cold Water Systems

PowerPoint 4: Requirements for Pipework Installations in Domestic Cold Water Systems

• This presentation outlines requirements for installing pipework in domestic cold water systems.
• The starter activity involved students creating 5 questions on the previous lesson's content and exchanging them with classmates.
• The lesson aimed to equip learners with the knowledge to classify five types of fluids, understand backflow mechanisms, and identify various backflow prevention methods and their applications.
• Insulation is the application of materials to prevent heat loss, gain, or frost damage.
• Effective insulation materials use still air, are appropriately thick, non-flammable, protected against vermin and drafts, impervious to moisture, and sufficiently robust for the task.
• Vulnerable pipework (e.g., outdoors, in lofts, under suspended floors, outhouses, 750-1350mm service pipes, temporary supplies, or near hot/cold pipes) should be insulated.
• Allowed materials include copper, plastic, barriered plastic, galvanised, stainless steel, gunmetal, brass, and aluminium.
• Materials disallowed include lead and any not listed on the WRAS (Water Regulations Advisory Scheme) approved materials list.

Fluid Categories

• Five fluid categories are presented.
• Category 1 (Wholesome Water): Mains water supplied by the water undertaker.
• Category 2: Water similar to Category 1 but with minor issues (color, odor, appearance, or temperature). Examples include hot water from cylinders, combi boilers, and softened water.
• Category 3 (Slight Health Risk): Fluids unsuitable for drinking but not significantly harmful. Examples include primary water, bath water, and shower water.
• Category 4 (Significant Health Risk): Fluids posing a notable health hazard due to toxic substances. Examples include microorganisms, pesticides, washing machine/dishwasher water.
• Category 5 (Severe/Serious Health Risk): Fluids that are potentially harmful with pathogenic organisms, radioactive materials, or fecal matter. Examples include urinals, sinks, WC's, bidets, grey water, medical rooms, laboratories, and abattoirs.

Backflow and Back Siphonage

• Backflow is the unwanted reversal of water flow, moving against its intended direction.
• This can lead to contamination and needs prevention.
• Back siphonage is the drawing of water back into an appliance due to negative pressure. It also requires prevention.

Protecting Category 1 Water from Other Categories

• To protect Category 1 (wholesome water) from Category 2 (possibly contaminated hot water), single check valves or non-return valves are essential.
• Protecting Category 1 from Category 3 requires double check valves or non-return valves, typically used under sinks, for filling heating system loops, or on outside taps.
• Protecting Category 1 water from Category 4 (contaminated water such as from a swimming pool) may necessitate specialized water treatment systems.
• Category 1 protection from Category 5 (foul water) necessitates the use of air gaps. These are found in CWSC, WC cisterns, basins, baths, sinks, and shower hoses.

Air Gaps

• AUK1 is the vertical distance from the WC pan's spillover level to the cistern's spillover level, typically 300mm.
• AUK2 is the distance between the tap outlet and the spillover level of a bath, basin, or bidet.
• AUK3 is the distance between the tap outlet and the spillover level on a sink.
• Flexible shower hoses need to be restrained from submersion in bathwater using a shower rail and hose retainer.

Water Regulations

• The Water Regulations cover the prevention of pipework freezing and excessive heat.
• A major regulation aspect is ensuring wholesome water remains uncontaminated.
• Correct use and positioning of backflow prevention devices are crucial for plumbers.

Review Questions

• The included questions cover insulation, backflow, back siphonage, the protection of category 1 water from different categories, and the functions of AUK2 and AUK3.