A few years ago my husband tied into the pluming for our bathroom sink to add laundry hookups. It's been working well, although occasionally some of the washing machine water will back up in the sink for a bit, but it hasn't ever overflowed the sink and the water was always clear. Last week we had a new roof put on our house and ever since then the sink has filled up every time I do laundry and overflowed twice- we have 2 kids under 2, so I do a lot of laundry. The water that collects in the sink has (what I believe to be) gravel sediment from the roof shingles, if that's even possible. What could be causing this & how can we fix it?

A few years ago my husband tied into the pluming for our bathroom sink to add laundry hookups. It's been working well, although occasionally some of the washing machine water will back up in the sink for a bit, but it hasn't ever overflowed the sink and the water was always clear. Last week we had a new roof put on our house and ever since then the sink has filled up every time I do laundry and overflowed twice- we have 2 kids under 2, so I do alot of laundry. The water that collects in the sink has (what I believe to be) gravel sediment from the roof shingles, if that's even possible. What could be causing this & how can we fix it?

Sounds like the roof guys didn't cover the vent and some trash got into your drainage system when they reroofed your house.
Rent a sewer machine, use a spade tip on the end and go down the lavatory vent if that's the one that vents the washer. Put out enough snake to get to the base and about 20 foot more. After snaking, cycle the washer to flush any debris that's left out into the city main.
Good luck, Tom