Kitchen drains into soil pipe or seperate gully

it is best joined to soil pipe, gullys block up with leaves etc.

Dear customer, I appreciate your trust in my knowledge. My answer to your query which is only my opinion this can be done both ways you have mentioned my choice would be to drill a 50mm hole through the external wall, approx 10 inches below the sink waste, then run a short piece of 40mm plastic pipe through it with a bend and a long piece of pipe running straight in to the gully. Make sure the gully is regularly cleaned. Doing this way will cancel out any chance of any bad smells returning back up the soil pipe and out of your plug hole but if you were to do it this way you would benefit from the fact it can't help towards blocking the gully, just don't put any food down the sink and it will be absolutely fine. I hope this information helps you in your project. Many thanks Neil askew.

Yes this is perfectly acceptable and will help to flush out any debris lurking inside your soil drains underground. 50mm hole through your back wall, 40mm push fit pipe and fittings into a strap-on boss connected into the soil stack, preferably into the top, but side is ok. Ensure you fit a proper sink waste ‘u bend’ trap to prevent any odours from the soil pipe. IF your soil stack is old and made of cast iron, then you’ll be best to keep your new kitchen waste separate and install a new gulley plumbed into your underground drain system. Good luck