I'm a newbie, if your one too then you need to check yours !
Having read through a few of these very helpful threads I checked my drains today, well 2 of them.
Outside one was running fine, Inside one was blocked with 3 pints of dirty mulch & water. Having no tool I found an old tap with a flexi Hose still attached and hey presto or 30 painful minutes later whoosh one empty chamber.
Gave the Pollen filter a clean & service while in there too. (the wife has the hair dryer optional extra which comes in handy there)
Thank you.