7 Hot Water Systems: Maintenance and Testing

Hot Water Systems: Maintenance Requirements

• Learners will identify and understand the maintenance requirements of hot water systems

Maintenance Requirements of Hot Water Systems Include

• Poor flow and pressure rates
• Expansion noise
• Thermostatic failure
• Immersion element failure
• Coil failure
• Cylinder fault
• Limescale issues

Questions to Consider

• Why is maintaining hot water systems important?
• What can result in poor flow rates?
• What can result in poor pressure rates?
• What tools test flow?
• What tools test pressure?

Soundness Testing for Plastic (Polybutylene) Pipes

• Slowly fill the system with water
• Inspect the system for leaks while filling
• Pump the system to the manufacturer's specified test pressure
• Check for pressure loss after 30 minutes
• Let sit for an additional 120 minutes
• Re-inspect for pressure loss
• System soundness is good if total pressure loss is less than 0.2 bar
• Avoid damaging the plastic pipe or O-rings during testing

Indicators of Poor Flow Rate

• Blockages or debris in the system can cause poor pressure and flow rate
• Reduced flow and/or pressure can conflict with manufacturer's instructions

Prevention and Solutions for Poor Flow Rate

• Check temperature settings on thermostat
• Clear limescale blockages
• Clean filters
• Ensure valves operate fully
• Lubricate parts
• Pipe sizes must be adequate

Expansion Noise

• Expansion noise occurs in hot water or central heating pipework
• Heated water expands the pipes, causing creaking
• The pipes can also creak as they cool

Solutions for Expansion Noise

• Inspect clips and brackets
• Inspect notching
• Inspect insulation and padding

Thermostat Failure

• Hot water temperature will be affected by this
• No hot water if the thermostat fails open
• Water temperature continues to rise to dangerous levels if it fails closed
• Both faults can be recognised and need careful inspection

Indicators of Thermostat Failure

• No hot water
• Water is too hot
• Cold water warming up
• Steam in loft area
• Open vent discharging

Immersion Element Failure

• No hot water results in a direct cylinder
• In an indirect cylinder, backup heat is required as the customer might not know

Indicators of Immersion Element Failure

• No hot water
• Fuse blowing
• MCB tripping
• Replace immersion and comply with Building Regulations Part P

Failure of Heat Source

• The primary heat source is commonly a boiler or immersion heater
• A green energy source could be the primary option
• Lack of hot water means check time clock settings and on/off switch
• Boiler repair requires a Gas Safe engineer
• Replace immersion and comply with Building Regulations part P

Coil Failure

• The CWSC pressure is slightly greater than the F&E cistern pressure if the coil fails
• Water forces into primary system, causing F&E warning pipe to discharge
• Hot water may be discolored after being drawn

Indicator of Coil Failure

• F&E overflow dripping
• Hot water discolored
• Replace cylinder with a current approved part L cylinder

Loss of Air Bubble

• This occurs in single feed or certain unvented cylinders
• Hot water is discolored if the cylinder has a single feed
• With an unvented cylinder, the pressure relief valve discharges when the water is heated
• Drain the secondary system to the base of the hot water cylinder
• Refill the system to reinstate the air bubble

Water Boiling

• Evident by steam in loft area, open vent discharging, and dangerously hot water
• Common when thermostats failed on old immersion heaters with the element still powered
• Replace older immersions with new immersions that are non self-resetting thermal cut outs
• Water will continue to heat if a cylinder stat fails, but the boiler stat cuts out at 80-85°C

Limescale

• Prevalent in hard water areas
• Causes blockages
• Jams components
• Reduces efficiency
• Causes unsightly build-ups
• Most noticeable when flow rate reduces in shower heads over time

Indicators of Limescale

• Reduced water flow
• Build-ups on draw-off points
• Stiff valves
• Install a water softener or scale inhibitor

Initial Checks

• Temperature settings
• Timer settings
• Fuse
• Water treatment
• Installation and connections
• Insulation

Hard Water Notes

• Temporary hard water causes maintenance problems in plumbing systems
• Calcium is lost and limescale formed, if hard water is heated above 65°C
• Limescale insulates water from the heat source
• Limescale causes blockages
• Treat hard water before it enters a domestic water system

Warm Water from Cold Taps

• Warm water coming out of cold taps can be caused by a hot pipe touching a cold pipe
• Warm water coming out of cold taps can be caused by the hot pipe being installed below a cold pipe
• A cold pipe should always be installed below a hot pipe to prevent heat gain

Knowledge Check Questions

• How poor pressure and flow rates can contravene the system
• Three things to inspect when there is expansion noise within pipes as they heat and cool
• Issue if a thermostat fails to open
• Issue if a thermostat fails to close
• Building regulation when replacing an immersion heater
• Stat cut out temperature if a cylinder stat fails and continues to boil