question about domestic sewers

[Tim Downie]

Our house was built in the early 70s and has a twin pipe system for rain water & sewerage.

We've a problem with the system backing up periodically that can be cleared by rodding with a rubber disk on a drain rod down a vent pipe that's situated between an inspection chamber in the drive and the main sewer in the road.

After rodding there is always some "water" visible down at the bottom of the vent pipe. Would I be right in thinking that there's some sort of bend/trap in the system at that point?

If there normally *isn't*, should I be able to rod through from the inspection chamber right past this vent pipe position towards the road?

It's not a major problem but clearly something isn't quite right and if there's anything I can do with drain rods rather than digging 6' down through the driveway I'd be interested to hear.

Tim

[Roger Mills]

There should be a U-bend where the vent pipe joins the sewer, so you won't be able to get your rods *into* the sewer from the vent pipe.

It's best to rod from the first chamber which isn't full, back upstream towards one which is. You can then loosen the blockage - which will be washed downstream and away when you pull the rods out.

If it keeps happening, you need to get a CCTV survey done to determine whether the pipe is actually broken and misaligned, or maybe blocked with tree roots. Quite a lot of repairs can be done by remote control without having to dig.

[Tim Downie]

Makes no sense with our system. The blockage is clearly distal to the chamber closest to the road. No point in rodding back up a clear system. There is no "chamber" at the vent pipe, just a small grate in the driveway with a 4" pipe beneath it. I can "plunge" this pipe vertically up and down but the rods don't progress in either direction.

I was just really wondering whether I should be able to rod through to the street sewer. From what you've siad, it seems not so I'll just carry on as I am at present.

Cheers.

Tim

[Roger Mills]

[Roger Mills]

[Try again - I hit send before I intended to, the last time]

There's *every* point in rodding up a clear system - in order to reach the blockage and dislodge it - but probably with a twirly fitting rather than a plunger on the end of the rods. If you start from a full chamber, it can be extremely difficult to find the outlet to get the rods started. It's easy from a clear one. Assuming there's a chamber where your sewer joins the sewer under the road, start from the road end.

I have a public sewer running under my garden which has got blocked many times in the 30-odd years I have lived here. When Severn Trent come to clear it they invariably rod - or more often jet - from a clear chamber back upstream towards the blockage.

[Tim Downie]

Nope. If I had an empty chamber downstream of the vent, I would be rodding it, believe me, but I don't. The sequence is: chamber - vent - street. The blockage (judging by the way that the fluid level is high in the vent pipe when the system backs up) is clearly between the vent and the street, a section that I don't can't rod without climbing down the sewer and rodding back up from under the street. (Somewhat outwith my domain I suspect).

Tim

[Roger Mills]

Well, you seemingly *do* have an empty chamber downstream of the blockage - albeit a public one. That's where I'd start! Do you really need to climb down into it - can't you wangle the rods into the end of the branch connection from street level? [If you *do* need to go down, it becomes non-trivial because, as soon as you've cleared the blockage, the chamber could start to (temporarily) fill up very rapidly - depending on how much volume is backed up].

With regard to whose domain it is, I'm assuming that it's a private sewer which is blocked - which means that the cost of unblocking it is down to you. If you employ someone to do it, they'll likely start from the street end - so why not do the same if you're D-I-Y-ing it?

If you don't want to do that, you could *try* rodding downstream from a full chamber but - as I said earlier - you'll probably have quite a job finding the outlet, to get the rods started. Unless there's a step in the pipe where the vent joins (unlikely), you should be able to rod straight past the vent junction.

[Tim Downie]

Please go back and read my first post. I'm fast losing the will to live (or at least explain *yet again* that there is no other chamber downstream of the vent pipe).

Tim

[Roger Mills]

You've clearly got all the answers - so why bother asking here?!

How, pray, could you 'climb down' into the sewer under the street if there isn't a chamber?

[Tim Downie]

I would call an inspection hatch that allows access to you drains within your property a "chamber". I doubt many folk would consider the sewer in the public road "a chamber". Nor do I imagine many DIYers climb down into the public sewer for the puposes of rodding their drains from "the bottom up".

Not saying its a bad idea, I just doubt that many folk climb down manholes in the street, crawl along the sewer (with a bunch of rods) and then try rodding their drains from below.

Anyone here done that? Does one have a right of access to the public sewers?

Tim

[Heliotrope Smith]

Is there a plugged off hole directly above the outlet in your inspection chamber in the drive?

[Tim Downie]

No. I can pass rods down from the inspection chamber towards the vent (& the street) but last time I tried, they wouldn't go past the vent. Is this normal or does it indicate a partial obstruction?

Tim

[Heliotrope Smith]

I would suggest that there could well be an obstruction in the vicinity of the vent. If there is a trap in your pipework then I would have thought that there would be an interceptor (bypass) that you could get at in order to be able to rod through to the public sewer.

If rodding for any distance then put the wheel or even nothing on the end of the rods rather than the rubber plunger.

[Roger]

The message from "Tim Downie" contains these words:

Not all public sewers are of large diameter. I can't see anyone managing to crawl along a 6" or even a 12" public sewer. :-)

The water co insist that my branch sewer is private right up to the point it reaches the main (12") sewer 10 or more yards down the road.

Some cheapskate private contractor with a drain sucking wagon lifted my triangular cover in the road and dumped the contents of his truck, including a load of plastic bottles and other plastic waste into the chamber below, which only had a 4" outlet. This blocked the outlet and the sewer eventually backed up to the extent that draining the bath one evening started to flood the kitchen. Luckily I heard the strange noise from the kitchen below and stuck the plug back in the bath before the majority of the water escaped.

The professional I got in initially tried water jetting from my manhole but quickly switched to the public sewer when he got nowhere fast. He had difficulty opening the manhole as it didn't have the normal lifting slots (which is presumably why the above mentioned cheapskate chose my sewer to dump his rubbish in). From the public sewer he eventually managed to force his water jet into my inspection chamber but every time he withdrew the hose the rubbish blocked the outlet again and he didn't manage to reduce the water level at all. (About 8 foot head in the chamber).

Next day they turned up with a gully sucker and, after trying again to jet the obstruction, sucked the chamber dry. The drivers mate had the unenviable task of climbing down into the chamber to remove the last of the litter.

[Tim Downie]

Good idea, I hadn't thought of that. I'll give it a go.

Tim

[Tim Downie]

Quite. Hence my querying the logic of the advice to consider the street sewer "a chamber" and to go down there and rod back up the way.

Yuck. Glad it wasn't my sewer. ;-)

Tim

[Tim Lamb]

And keep rotating the rod string clockwise or you may need to retrieve a set of rods as well:-)

regards

[Roger Mills]

I obviously don't know what your street sewer is like - but my foul sewer is

6" in diameter (and the surface water sewer is 12"). At each point where a private branch sewer connects into the public sewer there is a 'chamber' - about 2 metres deep and 1 metre in diameter, constructed out of interlocking concrete cylinders, with a heavy cast-iron triangular lid at road level. At the bottom, the main public sewer flows through as an open channel - and the branch comes in from the side. You can rod up the branch from road level - if you're sufficiently adept at steering the rods into the hole - without needing to climb down.

Do you not have anything like that? Have you actually *looked*?

[Tim Downie]

Not that stoopid. ;-)

Tim

[Tim Downie]

Oh silly me, there's a chamber there all along that I completely overlooked and failed to mention.

Go back and read my first post. Did I mention a chamber in the road? No. Guess why? Because there isn't one.

Tim