[Chicago, IL] After repeated maintenance calls regarding my kitchen sink, it overflowed and ruined my computer. I am withholding rent. Seeking advice.

I have had a problem with my kitchen sink spontaneously filling with dirty water from the drain. In other words, I am not using the sink at all and suddenly dirty water comes up from the drain, filling the sink and sometimes overflowing it.

I have reported to maintenance about 5 times within 5 months. They have come up to vacuum up some water but mentioned it's an old building and not much they could do.

Recently very gross water with dirt and debris came up and flooded my kitchen counter, kitchen floor and nearby carpet. I had a PC sitting on my counter, as I was using the counter as a stand-up desk. It got soaked and is ruined (it's a small PC and the motherboard is very close to the surface it sits on).

Apartment management says, "That's what renter's insurance is for," but submitting it to insurance is a $500 deductible, which is almost the price of the PC.

I told them that it is their pattern of negligence (i.e., not having a plumber actually fix the problem) that allowed this to happen. I am withholding rent until we come to an agreement. They have given me a 5-day notice and said they will have their lawyer proceed with eviction. It is my last month anyway (they have no security deposit), but I don't want a judgement against me.

What should I do? Should I submit the rent minus 500 and say that cashing the check constitutes payment in full? Or is this a lost cause?