Also known as a membrane, it is a boiler part that is normally located within the diverter valve or hydraulic section of the Ideal boiler. Its main purpose is to move a pin that then operates a micro switch which in turn sends a signal to the printed circuit board. The signal is normally to indicate the pump is running or there is a demand for hot water. They are sometimes referred to as the pump proving ? flow diaphragm or the domestic hot water DHW diaphragm.
Ideal 075487 Mini Disc For CH Hydraulic

Part: 075487

Price: £8.67
Ideal 075421 Mini Central Heating Diaphragm

Part: 075421

Price: £5.95
Ideal 075406 Domestic Hot Water (DHW) Diaphragm

Part: 075406

Price: £7.50
Ideal 173495 Diaphragm

Part: 173495

Price: £19.95