Rear window washer fluid leak

I have such a stupid issue that it makes me smile and sick at the same time. I don't know if I should consult a mechanic, an electrician or perhaps a plumber!



When I drive uphill up a significant incline, or when I park uphill, most of my windshield washer fluid leaks (sprays) out from the rear window washer nozzle.

When I am on a flat ground, both front window washer nozzles and the rear window washer nozzle work just fine - they spray with good force when I command them to, and they stop spraying as soon as I cease the commands.

I have been driving without windshield washer fluid for a few months now because it is almost pointless to pour it in the canister - I lose most of it whenever I climb up a hill ....

Does anyone have an idea what could be faulty here and what are the most accessible points in the vehicle to start checking them?

There is a small spring loaded one way valve inside the rear door in the pipe to the washer jet.
The spring has gone, the valve is a couple of pounds from Halfords etc.

The pressure from the pump forces water through, and when it stops pumping the spring closes the valve and stops it syphoning out the tank. It also keeps the water from running back-not that it would.

You can simply fit another one in the pipe where you can get at it under the bonnet, you may find then that the water in the pipe dribbles out down the door, and it takes a couple of seconds to start squirting.

I tried the remedy that the facade suggested.
I replaced the small in-line valve in the rear door with a genuine OEM valve, which I was careful to properly orientate.

However, the problem still remains the same.

What could I have done wrong or could something else cause the window washer fluid to leak out at the rear door whenever I drive or park uphill?

Another possiblity is that I got a faulty brand new OEM valve, but how to test if I am so unlucky?

The valve can be checked by blowing (or sucking) through it. One way it lets the air through and the other it doesnt

Martin