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COLD WATER ISOLATION (CWI) TEST
CWI test is a guide to showing the performance of the thermostat.
Prior to CWI test:
• Make sure that the temperature handle is aligned in the 40°C position.
• Make sure the supply temperatures are within the ranges 55 to 65°C for hot, & 5 to 20°C for cold.
• Unscrew the shower hand set from the flexible hose, & direct the water to be discharged into a
suitable vessel.
To perform a CWI test:
• Turn the product on using the flow handle, override the 50% economy flow stop on the handle & rotate
handle to max, giving 100% flow.
• The temperature handle button should be positioned at the 40°C nominal stop (parked).
1. Record the steady state temperature of both hot and cold water supplies. Note the Δt.
2. Record the temperature of the mixed water at the outlet, should be within range 40±1°C.
3. Isolate the cold water supply. If the flow ceases, CWI test passed. An ongoing reduced fine flow
of water (pencil stream) from the mixed water outlet is also acceptable as a pass.
Restore the cold supply & recheck the temperature at the mixed water outlet once stabilised.
If the flow has not reduced, the product has failed the CWI test. Product requires maintenance,
cartridge should be removed, cleaned & retested. See guidance below.
Additionally, clean all filters, ensure check valves are working, and make sure all isolating valves
are fully open. Refit the shower handset to the flexible hose upon completion of the test.
NOTE: In order to isolate the cold water & to perform the CWI test, service valves must be fitted (as
close as practicable to the mixer's inlets).
Volumetric guidance in the case of "ongoing reduced discharge of water" during CWI test
Acceptance criteria is as follows, isolate the cold water supply then:
1) Collect the water discharged from the shower outlet for 5 seconds.
2) Continue to collect the water discharged from the shower outlet in a second vessel for a further
period of 30 seconds.
The volume collected in the first period of 5 s shall not exceed 200 ml.
The volume collected in the second period of 30 s shall not exceed an additional 300 ml.
After restoration of the cold water supply (30 s) the mixed water outlet temperature shall not differ by
more than 2°C from the initial set mixed water temperature.
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MAINTENANCE NOTES
The fitting of isolation valves and strainers is required as close as is practicable to the water supply inlets
of the thermostatic valve. The thermostatic cartridge seldom fails and the possibility of blocked filters
should be investigated before contemplating replacing it. Small particles of debris may still find their way
past the strainers and onto the filter screens on the thermostatic cartridge. These should be cleaned and
re-fitted. See section cartridge replacement.
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