BMW screenwash non-return valve location

[9xxNick]

I have an F10/11 which has a short delay before the fluid comes out when first operating the screenwash after the car's been stood overnight. Subsequent washes are fine and come out of the nozzles immediately.

This leads me to believe the non-return valve isn't working properly.

Does anyone know where the valve(s) is located on this model? Is it integral with the pump or in the washer nozzles, or somewhere else?

[Neesser]

Have you solved this problem? How?

[9xxNick]

I'm working on it. Do you have the same problem, by any chance?

[9xxNick]

Right - the solution was to put some citric acid into the screenwash reservoir. The thinking that led me to this was that one possible cause was the non-return valve remaining slightly open due to chalky deposits in it caused by it drying out when the car was unused for a while.

Anyway, three days after the citric acid was added, the screenwash was instantaneous even on the first spray of the day, and has behaved perfectly ever since.

Citric acid is sold as a food preservative (easy to buy online) and is great for de-rusting tools or any rusty steel when made into a solution with plain water, which is why I had some.