Cant get the rear washer to work on my 850 estate. Pump definitely works. I have repaired the one-way valve which is behind the speaker panel on the pillar. Is there another one way valve somewhere along that pipe? Think I read something about a valve on the pipe beneath the carpet in the drivers footwell. Will continue to search for that post. Any help very much appreciated.

filter 

Can't say I'm familiar with the 850's washers, but on the 240/740 washer pipe I've found the small plastic pump adaptor for a football (not the needle type) is a good fit in the pipe. With a bike pump you can then pressurise the pipe to check for blockages. If your car footpump came with one of those cone shaped 'lilo' adaptors that should do equally well.

Check to see that your tyre well is not full of water. There's a union which seperates itself just above it and syphons water up from the reservoir and also leaks under pressure.

yes, the pipe had become disconnected near the spare wheel well, but I had already fixed this, and the filter looks fine too. I wonder if there is another oneway valve - perhaps under the carpet somewhere?

re rear wiper wash 

another common problem is the jet blocking up. i cleared mine by compressed air. disconnecting from the valve/connector inside the pillar (o/s)rear and blow compressed air through to unblock the jet outside. it is common cos it prone to corrosion. try it and let me know if that was the problem. it was with mine merry xmas evrybody!!!

There should only be one non return valve, located, as you've found, behind the OS rear speaker. If there is air in the system or the pump has run dry, some people in the past have found that it can take a bit of persuasion to get the water flowing again due to air locks in the system. You could try connecting a short piece of pipe to the filter outlet and operating the pump. This will get the water flowing without the back-pressure of the non-return valve. Of course, it may just be the most obvious - a blocked jet! Happy Christmas to you all.

yes i would agree with brian, seem highly likely to be an air lock at the pump ...i would remove the out let pipe at the pump and activate the pump, this should remove the lock... if this does not work remove the one way valve in the rear of the car and activate again.... mine often stops working after i have let the tank go empty but as im lazy these days i wait a few days for it to self-sort..... cheers jod