Should a clogged windscreen washer pump be covered under warranty?

The windscreen washer nozzles on my wife's 2014 Ford Focus gives hardly any output. It appears to be a common problem caused by a clogged filter on the windscreen washer pump. We have been quoted £75 (one hour labour) to fix this. Should this be covered under warranty - which runs out in October?
No because the problem is caused by slime growing inside the washer reservoir as a direct result of using poor quality screenwash. I've had this before on Ford and how I cleared it was to hold a hosepipe in the bottom of the washer reservoir then get someone else to turn on the tap. That blasts all the gunge out of the top of the reservoir.
Answered by Honest John

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