Foul drainage runs, a couple of questions

[Dreadnaught]

I have a first design for my foul-drainage runs (in red) from my engineers. A couple of questions…

1. Could I combine the two right-most ICs into one? It might mean one of the runs would intersect the IC at 90º.
2. Do the IC's all need to be 450 mm diameter or would smaller do, .e.g. 300mm or 320mm?

I ask as my engineers, more used to big civil projects, tend to over specify things I think.

(IC = inspection chamber)

 

Edited June 21, 2019 by Dreadnaught

[PeterW]

Lose them both, bring the connections past the under slab points and add a rodding eye on both ends assuming you have access to the back of the building ..? 

 

 

[PeterW]

Oh and move the downpipe on the right wall to the top right corner and run the surface water down the top and left sides not under the slab. 

[Dreadnaught]

Thanks @PeterW. Like this you mean … ?

[PeterW]

You don’t need the two parallel to each other to top right. One will be fine (and better as the flow is more consistent)

 

what is the one middle top..?? Is that just a stack vent as doesn’t seem to capture anything ..?? 

[PeterW]

And all your surface water ICs can be 250/300

[Dreadnaught]

2 minutes ago, PeterW said:

You don’t need the two parallel to each other to top right. One will be fine (and better as the flow is more consistent)

 

 

Makes sense.

 

2 minutes ago, PeterW said:

what is the one middle top..?? Is that just a stack vent as doesn’t seem to capture anything ..?? 

 

Middle top is the kitchen (the underlying plan is out of date).

 

1 minute ago, PeterW said:

And all your surface water ICs can be 250/300

 

Good news. Thank you. FW too or do they need to be 450 mm?

Edited June 21, 2019 by Dreadnaught

[PeterW]

Depends on depth tbh. Can you send me latest plans ..??

[Dreadnaught]

@PeterW, architect has not drawn the new now up yet, sorry. Only change in the plan will be the kitchen moving from west wall to the north east corner of the open plan kitchen/dining/lounge.

 

On invert levels, I think we have lots of play with. In the access road, the SW drain invert is 2m down. The FW drain invert is 1m down. Does that help?

 

[Dreadnaught]

Is it permissible to have junctions in FW drains under a slab, so long as all the runs are rod-able from rodding eyes, like this (bright green, with no IC's at the junctions)?

 

 

 

Edited June 21, 2019 by Dreadnaught

[PeterW]

Where is the front door ..???

[Dreadnaught]

@PeterW, front door is here…

 

[Dreadnaught]

Ah, how about this (bright green)… just two IC's, no rodding eyes.

• Both ICs are behind my dwelling out of sight but accessible (there is a 0.85 m path there next to the fence). 
• The kitchen could drain through the wall? Is that OK?
• This has an 18 metre  FW drain-run under the slab but it is largely outside the root zone. Is it too long? 
• I think the falls will allow it (my engineer can check).

Combined with moving the SW drain to the north side (thanks @PeterW), I have removed lots of the the trenches from the root zone. My tree officer will love me (or at least frown at me less)!

 

What do you think?

Edited June 21, 2019 by Dreadnaught

[Temp]

I think I would go with your first idea which was to merge the two IC into one (if the angles of the branches work out ok, you want to avoid bends between bottom of stack and IC).

 

 

[Oz07]

Why do architects also sometimes prefer showing Back Inlet Gully for basins/sinks rather than internal 4" drain coming up?

[Mr Punter]

With surface water, as long as you can rod / jet, the ICs are not considered important.

[Hobbiniho]

this is how i would do it if it was me, providing you have the depths to be able to do it, there is no need for loads of inspection chambers as long as you have rodding points as shown, you should not have a run that you cannot rod as you are talking about foul drainage you want to keep is simple, follow the "KISS" principle, straightest shortest route, least amount of joins nice shallow angles , your shyte does not need to do a full lap of your house 

[Dreadnaught]

8 hours ago, Hobbiniho said:

this is how i would do it if it was me

 

Thanks @Hobbiniho, I really appreciate it. I think I am learning the principles now:

• Access needed to every run. Inspection chamber if its a junction with multiple connections. A rodding eye if its a single run.
• Keep it straight and simple and minimise trenches under the slab where possible.

What I have not emphasised is that I have a preserved tree on the site, shown in the bottom left as a circle just outside the boundary. That gives a root-protection zone. The relationship with my tree officer will be improved if I keep the trenches out of the root zone, which covers the entire bottom-left corner of the plot. The point at which the services in enter the plot is in the root zone. This is unavoidable. The root zone is the reason that the around-the-houses scheme shown in bright green 5x posts ago and reposted below is the one I currently favour.  The advantages of the around-the-houses scheme are:

• Just three long runs. KISS
• All runs accessible from ICs
• Fewest ICs (one less than proposed by my engineer)
• Minimises trenching in the root zone (much less than before)
• Minor: all IC's out of sight around the back of the house.

Questions I still have:

1. Does it matter if a long-ish foul run (>15m) is accessible from only one end (like myright-hand most run in the around-the-houses scheme)?
2. While surface water ICs can be 200mm, how does one decide the size of a foul inspection chamber? 450mm vs 200mm, etc.?
3. Can I fit all my services in a single trench under an 850 mm path between my outside wall and neighbours fence? All services: foul drain, surface drain, electricity, gas, water, data.
4. Which is better. For a kitchen against an outside wall, take the drain through the slab or though the wall?

Note: my dwelling will be on screw piles so the fact that the wall of the house will be adjacent to this single service trench should not be a concern, I assume.

Edited June 22, 2019 by Dreadnaught