Potterton Performa 24 Installation And Servicing Instructions page 9

To ensure correct operation of the appliance and avoid invalidating the
guarantee, observe the following precautions
1. Hot water circuit:
if the water hardness is greater than 20 °F (1 °F = 10 mg calcium carbonate
per litre of water) install a polyphosphate or comparable treatment system
responding to current regulations.
2. Heating circuit
2.1. new system
Before proceeding with installation of the boiler, the system must
be cleaned and flushed out thoroughly to eliminate residual thread-
cutting swarf, solder and solvents if any, using suitable proprietary
products.
2.2. existing system:
Before proceeding with installation of the boiler, the system must
be cleaned and flushed out to remove sludge and contaminants, using
suitable proprietary products.
To avoid damaging metal, plastic and rubber parts, use only neutral
cleaners, i.e. non-acid and non-alkaline (e.g. SENTINEL X400 and
X100), proceeding strictly in accordance with the maker's directions.
Remember that the presence of foreign matter in the heating system can
adversely affect the operation of the boiler (e.g. overheating and noisy
operation of the heat exchanger)
9