I am laying some slabs in my garden, and I have a manhole cover which is a drain, so I decided to have a peek to see if everything was ok. There was some water in the bottom (as well as floating tissue), so I flushed my downstairs toilet to see if it flowed ok, and there was some flow, but the water still remains. I'm assuming there's a blockage as there shouldn't be any water yes? Should I just give some drainage company a call to see what they can do? I don't want it to get any worse