PIPES UNDER SINK

kayevajo

the pipe that leads to the drain thats under my sink , is full of water and i cant clear it , any ideas what it could be , as ive decking out the back and ill have to take up parts of decking to get at he drain

ive checked the u bend pipe and thats clear , ive tried

custic soda
drain clearer
white vinegar
snake like pipe clearer from woodies

thanks in advance

Cerco

If the U-bend is clear then I would be looking at the shore grill under the decking.
I had problems where the outlet pipe was very close to the shore grill and waste built up and needed to be cleaned out regularly.
I would lift a couple of decking planks and check it out. When replacing them cut out a slot in the planks and make an inspection point. You can re-use the cut pieces fixing the back with timber battens fixed to underside of planks around the cut out.
I would be concerned, if there is a build up of waste under the decking, that it might attract vermin. I think the products you listed would only give a short term solution if any.