I have lived in my house for many years, unfortunately its been the norm to have to continually open 3 chambers to proactively flush them out. If we forget to do so then I simply have a nastier, bigger smellier job each time - say no more.
So I know what the issue is, I just haven't actually got anyone to fix it properly - nor there seems to be any definitive answer hence me posting here to get wider expert opinions.
So for two of my inspection chambers (these are all 4 inlet ones) these are connected to toilets that are 1 or 2 floors above (1 has one toilet - hits it at 90 degrees, the other 2 toilets and bath waste, one toilet hits it at 45 degrees and the other 90). When the toilet paper and waste lands in the chamber it splashes across to the other side and sits there - the unused ones are not blocked off etc. For the one chamber that is highest up (fully accessible) it also hits the top of the manhole cover too, lovely!
The other one is near where they meet with the main drain. The flow from the toilets meets it at 90 degrees and again we experience the same build up of paper over time.
I have searched and searched and I can't really find a "product" that adequately helps - which would effectively mean that the chamber routes through without splashing into the unused chambers. I've heard people block up unused ones with cement or expanding foam etc.
Note 2 chambers are actually a metre down, only one is at a "workable" height of one riser.
Thanks - just trying to work out if I've missed something obvious and get clarity on the best way forward.