The WISA membrane (item no. 8050800311) is available from the recognized installer. Then follow the step-by-step plan for replacing a membrane in a WISA float valve with a foam float.

1. Shut off the water supply.
2. Open the reservoir.
3. If necessary, remove the float valve from the reservoir.
4. Remove the old membrane including the support plate.
   - Turn the locking axle a quarter turn up and remove it.
   - Remove the lever from the float valve.
   - Loosen the valve nut. If necessary, use a pipe wrench.
   - Remove the tap cover.
   - Remove the membrane (black) including the support plate (red or blue).
5. Place the new membrane.
   - Place the membrane with support plate on the valve cover. Note: The U-spout must point to the notch on the tap lid.
   - Place the tap cover in the tap housing. Note: The lug on the lid must fit into the recess in the tap housing. The U-spout is now downstairs.
6. Refit the float valve.
   - Screw the union nut onto the tap housing.
   - Place the lever with the two legs in the designated recesses on the tap housing.
   - Put the locking axle back through the lever and valve cover.
   - Tighten the locking axle by turning it a quarter turn downwards.
7. If necessary, place the float valve back in the reservoir, close it and open the water supply tap.