My kitchen sink is draining slowly, even thought the U-bend is cleaner than a clean thing.
It seems to be the case there's a partial obstruction between the U-bend for and the inspection cover outside. As the only thing that feeds into this outside drain are the kitchen sink, dishwasher and overflow for a condensing boiler; and even though we're pretty obsessive about not letting fat or grease down there, I suspect there's a build up of detergent, and some fat.
If it were fully blocked, I'd happily get my plunger and give it a good going over, but as it's slow draining, and there are so many vents feeding into it, that's no use. I have tried snaking it, but that has only really ensured there's a 1/4 inch (out of a 1 3/4 inch plastic pipe) path for the first 6 feet - it doesn't feel like there's any really obstruction; Similarly, I'm able to push a hose pipe up from the inspection cover up towards the kitchen until it meets the point where the 1.75" pipe meets the 3" foul drain (I can hear the end of the hose tapping against the end). Any water jetted up from the outside flows away with no problem, and after a bit of work, is flowing clean.
I'm at a loss as to how to clear the rest though, so the drain runs clearly, and without backing up the overflow for the central heating and out into the cupboard under the sink.
Are there any options other than calling a plumber out, who may have a longer / larger bore snake?