Hot-Water Line Failure at a Small Clinic
A small clinic in Nagpur adds a hot-water line from a 15 L electric geyser to two wash basins. The geyser thermostat is set at 70 °C and the line is about 15 m long, mostly concealed in a wall. The plumber used 25 mm UPVC pipe, ordinary PVC solvent cement and brass threaded nipples screwed directly into the UPVC. He supported the pipe at 1.2 m intervals and made no expansion loop. Three weeks later, the joint at the geyser outlet has softened, a hairline crack is weeping, and the pipe has sagged between two supports. The clinic manager wants the same plumber to apply more cement and wrap the joint with PTFE tape before an inspection. The geyser's safety valve is set at 8 bar, and the static water pressure is about 3 bar. The manufacturer's CPVC data sheet is available but has not been read.
1. Identify the material and jointing errors and explain why the repair proposed by the manager will fail.
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UPVC is not suitable for a continuous 70 °C hot-water line; its strength falls sharply at elevated temperature, and it is normally limited to cold water or low-temperature applications. Ordinary PVC solvent cement is not the specified cement for CPVC hot-water pipe, and threading UPVC directly with brass nipples concentrates stress and invites cracking.
The 1.2 m support spacing may be too wide for hot CPVC, and no expansion loop was provided, so thermal expansion has added load at the geyser connection. Applying more cement and PTFE tape only covers the crack; it does not restore the pipe's temperature rating or relieve expansion stress. The joint will continue to weep or fail under pressure.
2. Specify the correct replacement and testing procedure.
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Replace the exposed hot-water run with a pipe rated for at least 70 °C at the system pressure, such as CPVC or PPR. Use CPVC-specific solvent cement with the correct primer and cure time, or the manufacturer's approved jointing method. Transition to brass or metal threads with proper transition unions; do not thread the plastic pipe directly. Provide expansion loops or offsets, and support at the manufacturer's spacing for hot pipe.
Isolate the geyser, flush the line, and pressure-test with water, not air. Test at 1.5 times the maximum working pressure or the manufacturer's specified test pressure, whichever is higher, for at least one hour. Check the geyser safety valve and set the delivery temperature with a thermostatic mixing valve if the clinic needs safer hot water at the basin.
3. What commissioning checks and user instructions should be given after the repair?
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Run hot water and check for leaks at every joint, especially at the geyser outlet and transition fittings. Confirm that the pipe expands freely and does not rub against the wall or support. Check that the safety valve discharge is piped to a safe drain and that the geyser thermostat and over-temperature cut-out work.
Measure the hot-water temperature at the basin and adjust the mixing valve so the user is not exposed to 70 °C water. Label the hot line, record the test pressure and duration, and tell the clinic not to wrap leaking joints or raise the thermostat without checking the pipe rating.