Replacing Whole Sewer pipe

[rizla01]

Hi all.

I have two inspection chambers and between the two (Approx 5Mtrs) a tree root seems to have broken in causing a blockage every 4-6Mths.

As I fear this is likely to get worse, not better, my plan is to replace ALL of the pipework between the two chambers with one continuous length.

And, being lazy (Old) I am paying someone else to dig out the soil.

I expect that I should be able to remove old pipework and dig about 4 ins below and lay some gravel, knock out the cement from inspection covers and feed new pipe in having first cut end off at an angle (approx 45Deg?)

I am planning on mortaring in the two ends using quick drying cement.

Does this sound about right?

Any advice before I start?

Thanks

 

[Hugh Jaleak]

I'd cut the existing pipe outside the chamber(s), leaving a 'stub' of about 4-6 inches to connect onto. Trying to join new to old inside the chamber may lead to problems, you may be faced with a size difference between new and old pipe which will cause a 'lip' at the joint, ideal position for material to catch and build up. You'd be getting rid of one problem causing blockages only to create another....

Use suitable connectors (e.g. the 'Fernco' type) to join new to existing, and the drain can be used immediately. Bed pipework on peagravel, then once desire fall is ascertained between the chambers (make sure there are no dips!), cover the pipe in gravel, initial layer of backfill needs to be free of any large or sharp stones/big lumps of clay etc.

 

[big-all]

is it a shared drain??
if so its you local authority housing trust or waterboards responsibility
shared means 2 or more properties use the same drain

 

[rizla01]

I'd cut the existing pipe outside the chamber(s), leaving a 'stub' of about 4-6 inches to connect onto. Trying to join new to old inside the chamber may lead to problems, you may be faced with a size difference between new and old pipe which will cause a 'lip' at the joint, ideal position for material to catch and build up. You'd be getting rid of one problem causing blockages only to create another....

Use suitable connectors (e.g. the 'Fernco' type) to join new to existing, and the drain can be used immediately. Bed pipework on peagravel, then once desire fall is ascertained between the chambers (make sure there are no dips!), cover the pipe in gravel, initial layer of backfill needs to be free of any large or sharp stones/big lumps of clay etc.

Firstly the sewer pipe is entirely on my property.

Having purchased the pipe and collars to do a quick fix I noticed (Dunno why I didn't see before) that it is not clay pipe but the dreaded Pitch Fibre.

It is approx 60 yrs old so I feel that it should be removed completely and replaced with PVC pipe.

On even closer inspection I note that the two manholes are just concrete bands with a gulley laid on mortar (I assume) and then mortared up around the sides.

Where the pipe enters I assume it just sits on a collar so hopefully I will be able to remove the concrete and pipe OUTSIDE the collar and insert the new pipe into the collar. Failing that it will be a 4" angle grinder to cut the gulley back a bit.

What I am not totally sure of is sealing the PVC pipe into the manhole.

If it is bedded on concrete and then concreted over will that suffice or should I use some waterproof rubberised sealant?

Thanks

 

[Hugh Jaleak]

Concrete will suffice, make it a fairly strong mix. Final finishing off for benching should be a strong mortar mix. (Water will soon wear away a weak mix.) As said, it is fairly vital to achieve a smooth joint between the new and old, to avoid any edges where material can catch. Use mortar to finish any gaps to a smooth edge.

Traditional brick (or concrete sectional) chambers relied on the concrete base to hold everything in position, the brickwork was built up from this, then benched to provide a smooth finish internally. On big sewer jobs it is a full time occupation for someone just benching manholes!

 

[rizla01]

Excellent Hugh,

Should get sorted this weekend.

Thanks