Prepare the location
Check the seating of the new cistern. The base should
be firm and supported by a platform built across the joists.
The platform should be nailed securely to the joists.
Commence plumbing in the new cistern
75mm (3 inches) below the top of the cistern cut a
hole for the float valve to pass through. Put a plastic
washer onto the tail of the float valve and pass it through
the hole. Place the reinforcing plate onto the tail, then
another washer and a fixing nut. Now tighten the fitting
with your fingers until tight. Then use two spanners to
tighten the fitting. A tap connector should now be screwed
onto the valve, ready for the connection to the 15mm (0.5 inches)
Drill a second hole 25mm (1 inch) below the inlet for the
float valve in order to connect the overflow pipe. Pass
the connector through the hole. Now fit a washer and tighten
its fixing nut on the inside of the cistern. Fit the insect
filter and the dip pipe. A length of plastic overflow pipe
needs to be attached to the assembly, run to the floor and
then to the outside of the house, where it must be positioned
in a conspicuous location. It is important to check the
positioning of this pipe as continuous fall must be maintained.
Drill holes 50mm (2 inches) above the bottom of the cistern
for each tank connector, to the hot water cylinder and the
cold taps. Push the tank connectors through each hole with
one polyethylene washer on the inside. Wrap a couple of
turns of PTFE tape around the threads and fit the other
washer. To stop the tank connector from turning, screw on
the nut, but be careful not to overtighten as you could
damage the washer and this could cause leakage. At this
stage it is prudent to fit a gate valve to each distribution
pipe. This will enable the you to cut off the water supply
without having to empty the cistern.
Check the alignment of both the rising main and the distribution
pipes to the system before connecting with compression fittings.
Remember that if the cistern is plastic, soldered joints
Clip all pipework to the joists to avoid movement as water
passes through the cistern. Open the main stopcock, checking
for leakage as the system fills. The float arm needs to
be adjusted as the level of water rises, to maintain a water
level 25mm (1 inch) below the overflow outlet. The vent pipe
from the hot water cylinder should be adjusted to pass through
the hole in the lid.