ORG and concrete pathway

Hi all,

Recently moved to a newly built home and we had a concrete pathway poured around the perimeter.

Aside from being unhappy with the overall job due to lack of control joints causing shrinkage cracking almost right away, and a lack of expansion foam use, I have noticed another issue after reading some threads on this forum.

It looks as though the ORG has been set as a regular storm water drain level with the concrete but just with a domed grate.

Furthermore, I actually think the ORG may be a completely different pipe than the one with the domed grate. Would I be correct in thinking the ORG would be the pipe I can hear water running in when the shower or sink is being used.

Thanks in advance for your assistance.

Use of expansion foam is not mandatory but it's use is considered to be best practice.

It is up to the tradie's best judgement as to the height of the pipe's invert when it is fitted to an impermeable surface but the overriding requirement is that it must not allow surface water ingress into the sewer system. A concrete path must have a minimum slope away from the house over the first metre, the slope depending on the area's rain intensity. See below...

NCC 2016 Building Code of Australia - Volume Two Page 112
SITE PREPARATION
3.1.2.3 Surface water drainage
Surface water must be diverted away from Class 1 buildings as follows:
(a) Slab-on-ground — finished ground level adjacent to buildings:
the external finished surface surrounding the slab must be drained to move surface water away from the building and graded to give a slope of not less than (see Figure 3.1.2.2)—
(i) 25 mm over the first 1 m from the building in low rainfall intensity areas for surfaces that are reasonably impermeable (such as concrete or clay paving); or
(ii) 50 mm over the first 1 m from the building in any other case.

The height of the pipe's invert therefore depends on the path having a compliant slope and its position on the path. If for example the path had no slope or was in an enclosed area with a risk of flooding, the invert would need to be higher than one positioned on a good slope and well drained area. Because there are these variables, a regulation stating a minimum height above a concrete path is not feasible and there is also the consideration to not invite a tripping hazard on a concrete path.

There are also very important additional regulations about the minimal separation heights between the ORG's invert and the bottom of weep holes. I have seen many photos on this forum that have shown extreme non compliance with weep holes sometimes even partially covered by a concrete path with little apparent slope and a high ORG (even though the ORG has been fitted as low as possible to the path). The last thing anyone would want is to have the ORG overflow and sewage pass through the weep holes into the wall cavity but it happens.

Re the domed grate, it is important that the cover lifts off easily.

Yes, the sewer pipe transports both grey and black water.

Thanks for the reply.

I've got a photo which shows 2 drains.


https://ibb.co/0FRBLwp

The drain further away up the side of the house has the dome grate on it.

The drain close to the corner is the drain that I can hear running water in when the shower or toilet is used.

Any advice on what I can do?

Thanks very much.

Where are you located?

Do you have photos of the pipes during the build?

Southeast suburbs Melbourne.

I may have photos on an old phone.

From memory the concrete slopes to the drain where i hear the water. If that is actually the ORG what can i do?

The domed cover is the ORG. There had to have been a reflux valve fitted in the sewer pipe because of the ORG's height. Not sure that the VBA would be too happy with the ORG's height.

The drain closest in the photo should be the surface water / storm water drain, you shouldn't hear grey or black water flowing through it.

I can't see how a plumber could possibly have connected some DWV grey and black water pipes to the stormwater as he could not possibly fail to notice the difference between 90mm pvc stormwater pipe and 100mm pvc DWV pipe plus different connections are needed to adapt the DWV pipes to stormwater.

Can you see the water if you shine a light down there? If you are sure the toilet flushes down there, you could put some bright food dye or even some cordial in the pan and flush to confirm it.

A 90mm pvc storm water pipe is measured as an outside diameter and the wall is 1.9mm thick.

A 100mm pvc DWV pipe has a 110mm outside diameter and 4mm thick walls.

Thanks for the reply. I have just had look down the drain and can confirm that when i run a tap or flush the toilet, nothing is happening in the drain with the dome grate. There appears to be stagnant water in there.

It is the drain on the corner where i can hear and see water running. If i look in there with a torch i can see a pipe joins in there about half way down where the water enters and falls to the bottom and into a corner.

I'm concerned now

Were both stand pipes already there pre path? The ORG (domed cap) would have been there at least.

The water you describe in the domed grated pipe will be a trap.

This would not be the builder's responsibility unless the builder arranged the concreting but maybe as a client, they could do an inspection for you. Alternatively, you could contact the VBA because there are several concerns including the ORG's height and the small separation between the finished ground level at the ORG and house floor level plus what you have noted. I have no idea about what is going on with that closest drain but it is certainly 'interesting'.

Can you confirm that the domed grated pipe has a 100mm DWV pipe (the grate should easily lift off) and that the closest pipe is a 90mm thin walled stormwater pipe thanks? I have a nasty feeling that the two grates are on the same DWV pipe.....but surely not???

Is there a slope on the path away from the house?

The pipes were there pre pathway.

There is a slope away from the house.

What did you mean by the separation between the finished ground level at the ORG and the house floor level?

I can't get any help from the concreter as long story short they got their back up at me big time regarding me wanting help with the cracks.

I'm not sure i can contact the builder as they will likely push any blame onto me stating non compliance and void any warranty

I will check the pipes and get back to you with a size.

Photo of the drains pre-path.

The domed one is an ORG.

Was the surface drain (nearest pipe) already there? I am wondering whether the concreter has illegally tapped into a sewer pipe to connect a surface drain, something that would be looked on very, very seriously by the VBA.

The concreter shouldn't get too narky because there is also suppose to be a minimum height of 75mm between the path and the damp proof course (bottom of the weep holes) for compliance.

I would be sending the VBA a report with some photos and ask for an inspection.

The pipes were already there before the concreter started work.

I'm concerned about getting the concreters involved again as i was basically threatened by them last contact

The nearest drain will collect surface water but you confirmed that it drains grey and black water. If it does, it is highly illegal and you can't leave it like that.

If the nearest pipe's outside diameter is 110mm, it is a DWV pipe.

Maybe contact Metropolis Solutions for a professional onsite inspection and advice so you know for sure what is going on.

http://metropolis.melbourne/