Waste pipe blockage because of drop?

[RSAH94]

Hi,
I'm not a plumber so I need some info/advice...

I recently renovated a bungalow, which has all gone well and isn't the problem, but since moving in our drains block. The first time severn Trent came out and unblocked them, but said they shouldn't really be doing it as its on our driveway.
After unblocking it myself with plumbers rods nearly every month, iv noticed it blocks in the same place, on a T that joins the main road. It starts with a bit of toilet roll that builds up and eventually blocks 8 meters of pipe with solid Rubbish and TP.
I have also noticed that over the 8m the water doesn't flow well when unblocked, and iv measured it, and there is only a 60mm drop over 8m of waste down our drive.

Basicly I'm fed up of my drains blocking and is there anything I can do?

Sorry for the long sob story
Cheers!
R

 

[Ric2013]

Hi Rob,

You have a 1 in 130 drop. Assume you've measured that with a water level or something. It's not a lot, but unlikely to be the problem. I read an interesting study of various drains and drops and you could go down to 1 in 1000 and beyond without it creating blockages. Basically, as long as it didn't start running uphill.

Most likely there's a badly executed joint at that T which is rough, roots have got in, or there's a breakage that has caused a step. Something is snagging the solids. Which you have already noticed. If you're really lucky, it might just be a blob of mortar you can knock off in a bit of CCTV-assisted keyhole surgery, but it would be reasonable to assume the drain hasn't been problematic ever since first laid.

If the bad bit of tee joint is shared, you may find the actual defect is on a pipe you don't own. Could be the water board's if it's adopted the shared drains. So you need to push for attention. On the other hand, if it's solely yours then I think if you can cure the specific defect, that'll be the end of the matter. Nice summer project for you?