Sewage / Grey Water

[Onoff]

Not sure where to start on this one...

My house is quite "wide". The bathrooms and toilets are on the LHS. The 3 toilets go into a clay soil pipe run then to a cess pool down the garden. The bathrooms grey waste from sinks, shower & bath just exit onto the garden between house and boundary.

The kitchen is on the RHS of the house and the grey waste runs on the surface in just a 1.5" waste pipe.

Third World? Oh yes! The previous owners discharged the grey water onto the garden as they "didn't want to fill the cess pool up".

You can just see the white kitchen waste at the bottom of the black down pipe:

The kitchen grey water discharges in a bit of garden where the mound of soil is now beyond the bamboo:

The black, rainwater downpipe did come underground to an ad hoc a soakaway to the LHS of the garage. I think roughly where the concrete ornament is in the above photo.

At the mo then the kitchen waste and rainwater is going straight into my new trench.

With the trench open as it is I'm mulling laying some 110mm underground soil and appropriate bends & branches. Primarily so I can have a WC in the garage later.

But where to start?

Then, must this soil pipe sit on pea shingle to falls? I've run out of pea shingle basically so it'd mean getting some more in.

 

[Smallfry]

looks pretty simple to me ..........

Run the 110mm soil pipe from the garage (green trench) right across to the existing clay soil. Tee all the grey water into that, then tee the new soil pipe into the clay soil.

If it were me, I would replace the clay soil to make this easier, and it may be necessary to get the appropriate fall across the system depending on how deep existing clay soil is.

Mains water can be run above it is deep enough to avoid frost.

Leave the rainwater as is, OR discharge on surface further away (we do) either way, do not discharge into cess pit, as there is a risk of overflow.

What is the cess pit made of ? Ours is brick, and it has not been emptied for 40 years ........

Should by rights all be in shingle, but as no one from Building Control will be inspecting, it is up to you, but I would, to save any possible hassle.

I see you have a digger then !

 

[Onoff]

looks pretty simple to me ..........

Run the 110mm soil pipe from the garage (green trench) right across to the existing clay soil. Tee all the grey water into that, then tee the new soil pipe into the clay soil.

If it were me, I would replace the clay soil to make this easier, and it may be necessary to get the appropriate fall across the system depending on how deep existing clay soil is.

Mains water can be run above it is deep enough to avoid frost.

Leave the rainwater as is, OR discharge on surface further away (we do) either way, do not discharge into cess pit, as there is a risk of overflow.

What is the cess pit made of ? Ours is brick, and it has not been emptied for 40 years ........

Should by rights all be in shingle, but as no one from Building Control will be inspecting, it is up to you, but I would, to save any possible hassle.

I see you have a digger then !

The trench went in at 750mm deep with a 6" bucket. Next bucket up was 18".

I lined the trench bottom with pea shingle, laid a 63/50mm blue water pipe duct and covered it up again with shingle. I've left that upturned and capped each end (so I can find later and trench up to it). The blue duct only runs the length of the trench (it was an offcut of duct, just about the right length). It would need to be extended to the "clay" run on the left and garage on the right along with extending the trench. Thus provision is in for the "water" to be at nom 750mm deep which should guard against frost

On top of that I put my 63/50mm black electrical duct and again covered with pea shingle.

So now I've a trench partially filled with rain / grey water and electric ducts but yet to be backfilled.

What's a reasonable fall for soil pipes, I'm reading differing things? The garage is built a tad downhill so the trench from there slopes uphill a bit. Thus at the garage end the soil pipe might need to be close to the surface and under slabs etc.

The trench where it bends right off to the garage:

How the ground slopes up from the garage:

From the garage up to the bend:

I want the garage soil exit a little further along the garage so will extend the trench rather than use the one where the black electric duct is.

Is the lower idea best? Kitchen drops into the main run via a bend and swept T?

 

[Agroshield]

1:40 to 1:80 is considered OK for foul.

Pea shingle is used so it does not puncture the pipe. It is easy to shape to form a nice bed for the pipe. It does not compact/settle once the pipe is laid on top of it.

Any material that achieves the same aim will be OK. That might mean a rudimentary screening of the excavated material to remove sharp bits.

Excavated soil to form the pipe bed might be less easy to shape and also will compact.

For a large height difference, a proper setup mimicing your pencil sketch would use a backdrop manhole (with a removable cover to access the lower run), with rodding access to the upper run.

Another option for a lower height differnce is to lay most of the incoming high level run at high level and then a steep fall to the last 1m or so, with 45 degree bends (i.e. a ramp).

A 45 degree tee at the lower level is a good idea (you have written swept tee but drawn a 90 degree tee).

 

[Onoff]

Just sitting in Selco's cafe waiting for my order. Right or wrong I ordered these bits but I'll likely change the M/F 87.5deg bend to a F/F bend:

It'll have to be all in one ballast for bedding as that's all I have. Just hope I've enough of that even!

This lot should at least see this section of the trench completed and back filledby end of tomorrow.

 

[Smallfry]

As said, 1 in 40 to 1 in 80 is the norm. You dont want the fall to steep because the water will drain too quickly and leave the unmentionables stranded, which will lead to blockages. I usually aim for 1 in 60 or thereabouts, and try to make the run as smooth as possible with no dips.

Either way illustrated will be fine, but always use swept bends or 45 degree tees. Another thing you might want to consider is a rodding eye.

Building regs would insist on it, and TBH it does make things easier if there there is a blockage

 

[minimutly]

1:40 to 1:80 is considered OK for foul.

Pea shingle is used so it does not puncture the pipe. It is easy to shape to form a nice bed for the pipe. It does not compact/settle once the pipe is laid on top of it.

Any material that achieves the same aim will be OK. That might mean a rudimentary screening of the excavated material to remove sharp bits.

Excavated soil to form the pipe bed might be less easy to shape and also will compact.

For a large height difference, a proper setup mimicing your pencil sketch would use a backdrop manhole (with a removable cover to access the lower run), with rodding access to the upper run.

Another option for a lower height differnce is to lay most of the incoming high level run at high level and then a steep fall to the last 1m or so, with 45 degree bends (i.e. a ramp).

A 45 degree tee at the lower level is a good idea (you have written swept tee but drawn a 90 degree tee).

Don't underestimate the tendency for fats to aglomorate (is that the word for sticking together?) in the waste pipe, it can completely clog a 1.5 pipe. Daughters had hot caustic more than once, but eventually I had to resort to the sledgehammer to break open the footpath and dig out the pipe - it took full mains water pressure to move the lump of lard.

 

[Onoff]

Just popped out in the dark with my trusty Clas Ohlson bargain laser level and dic some rudimentary surveying.

Measured from the laser line/datum to the ground then the base of the trench. The main trench has a fall of about 1 in 91. Not the end of the world as I have depth to raise the right hand end. The short trench to the garage does indeed slope downward might just do it if I have the soil pipe under paving slabs behind the garage / raise the ground a tad or do a French drain.

 

[addjunkie]

You want long radius bends in sewage/grey water.

These come in useful joining plastic and clay

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[Onoff]

There's 11m of soil pipe buried alongside the path here. It ends where the blue duct is poking up.

This unmade patch of ground is where the kitchen grey water has traditionally emptied into. It'll have to stay like that for a while.

You can just see where the 110mm comes up out of the trench. Ready for when I connect the kitchen waste into it sometime.

I've never had a proper path to the garage. Jus to a few haphazard slabs laid on the mud.

Tempted to put some gravel boards in set 3' apart and fill up with flints as I come across them. Maybe a length of weed fabric down first...