First it's a two man job.
These are possible causes I've come across in my building days.
Cooking fats/grease, excessive amounts of toilet tissue, Sanitary towels, Disposable nappies. The worst senario is a partially collapsed pipe. I had one and replaced it with a lot of digging to get to it.
This is where the other Fella/Sheila comes in open the manhole you find and get someone to flush the toilet while you watch for the flow and note it's direction, you'll see why later.
If the right manhole and it's clean then replace the cover and now go back in the house because it's a waiting game. Now you will have to wait for it to block up again.
meanwhile who ever flushes solids and tissue have to note [sounds funny] the amount of tissue used.
Who ever uses the toilet and flushes solids and tissue and causes the blockage and the tissue count is high then that could be the cause it's blocking on the P trap or S bend of the pan. Now check the manhole while it's still blocked and see if the manhole is clear.
IF Yes! then the blockage is either the tissue ins the P or S bend or a partly blocked pipe to the manhole. Free the blockage by use of a plunger or a strong mix of boiling water and caustic soda. Use rubber gloves when handling caustic soda or it'll burn hell out of the skin. One person must be checking the manhole while the other is clearing the blockage and when it clears watch and note how fast the flow is. if it's clears the pan but runs slow through the manhole the blockage is in the pipe work so rod the section between the manhole and toilet as far as you can get the rods with the worm head on the end. Take note only turn the rods clockwise, if you turn them anti clockwise they will unscrew and you will loose them. A tip is to join the rods and wrap the joints with duck tape. Pull the rods out and check if anything is on the worm.
But on opening the manhole you find the manhole itself is full or half full the blockage is then between that manhole and the next manhole or road sewer. if there is a second manhole, usually in the front of the property inline with the first and it's clear then push the rods up that one towards the first manhole that's blocked and if it's in that streach wait for the sudden gush if you manage to release the blockage.
if it still keep blocking and you know it's not the amount of tissue then it could mean a CCTV check to see if the sewer pipe has partially collapsed. You need to keep a bucket of disinfected laced water by you at the manhole so you can wipe the rods down after.
Good luck it's a messy job.
Bob
Bob, November 2005
