Question on foul drain / adding storm water drains

[damanpunk]

Hi fellas,

I'm trying to plan out the drains for my garage and I'm looking for a bit of help. My house was built in the 70's and I'm 99% certain it has a combined drain/storm water pipe run. My reason behind thinking this is that there's only one manhole and under the cover only one inspection area. I also found some backed up waste at the bottom of the rowan pipe outlet (floor wipes etc) that matches what caused a blockage originating from the soil stack.

This drain runs down the east side of the house going south/north. My garage is going to be built on the west side of the house so I'll have two rowan pipes that will need to be connected into the existing drain at north/south ends of the garage.

As the runs back to the main drain are only rain water (and perhaps a drain from a sink in the garage) can you get away without inspection/rodding points? Or even less of them? Are there no limits on what angle the pipes can enter the existing pipes? In theory only water will be able to enter the system as the rowan pipes will be fitted with those rubber bungs to ensure a seal at ground level.

Can anyone point me towards some info on the subject?

Any help is most appreciated

Also I can stick a sketch up tomorrow if required when I'm at my autocad machine!

 

[pinenot]

The rhone pipes may be connected to a sump as apposed to the sewer (but I doubt it on a 70's build) worth checking with a neighbouring property if poss.
Could you post a sketch, both of the proposed drain runs from the garage and the existing drains...pinenot

 

[damanpunk]

Hi Pinenot, sketch attched.

I have two different options on it. Option A would have the drainage running underneath the slab and connecting into the existing drain at the rear of the house. This seems like the simplest option but I'm not sure if the drains are deep enough to accomodate two falls (fall from front to back of garage and fall from garage to east side of house)

Option B runs underneath the slab with the fall going in the opposite direction, it then travels across the drive/garden and meets the existing drain run. Maybe slightly more chance of success with this option as the falls are easier to accomodate as the houses are built on a hill and this is following it's natural slope.

Either way what would you recommend rodding/inspection wise for either option? With it being a shared foul/storm drain and having already found backed up waste in one of the rowan pipes I should be having inspection points at each change of direction and at the bases of the rowans?

 

[AdamCH]

Hi fellas,

I'm trying to plan out the drains for my garage and I'm looking for a bit of help. My house was built in the 70's and I'm 99% certain it has a combined drain/storm water pipe run. My reason behind thinking this is that there's only one manhole and under the cover only one inspection area.

My house has separate foul and rain but only has a manhole on the foul. My house was build a 1958 so bit before yours. Easy to test though by putting the hose pipe down the rainwater gully and seeing if you get water at the manhole. Try more than one rainwater gully though in case someone has connected one to foul in error.

 

[damanpunk]

I'm getting one of the blocked drains fixed on Wednesday so I'll check that afterwards

Any feedback on the potential options guys?

 

[pinenot]

Could you put the N arrow on your sketch to verify runs/orientation etc.

 

[damanpunk]

Ah sorry, I can mark it but it wouldn't be till tomorrow. North is at the top of the pic tho i.e. a car would travel northwards onto the drive.

 

[pinenot]

I'm posting your sketch back with some of my own additions re drain run direction and front of property (S) downpipe and under slab run, can you let me know if they are correct...pinenot

View media item 59387

 

[damanpunk]

Hi pinenot,

Here's the sketch with a north arrow and indicating the slope of the site. The sewer is at the bottom of the front garden

 

[pinenot]

I find it strange that the rodding point, indicated on the sketches, is located after all your connections! the whole reason for rodding points is provide access upstream of any blockage. In your situation you would have to rod in the opposite direction which could be problematic.
No matter this can now be resolved in the new layout. Iv'e put this together hope it helps - View media item 59400...pinenot

 

[damanpunk]

Haha unfortunately it's very much so the 'house that the 70's built', when I say that I mean they were probably off their faces on drugs!

That layout you've drawn makes sense and would certainly be the least hassle as I'm re-doing the garden/drive anyway.

I'll have a water cylinder, system boiler, sink etc in the garage too at the rear. Do you think it's worth running a drain underneath the slab too or would you just branch out drains through the wall and down into the pipe? Building control shouldn't give me any grief I'm guessing as it currently appears to be a combined system? I'll double check it anyway once my blockage is fixed.

Also this may be a daft question but I'm guessing that single rodding point is only required to rod north/south as the soil stack is downstream of it? and the storm drains will never require rodding?

I think I'm 'starting' to get the hang of this, hopefully

 

[pinenot]

Yes mate, your correct re the rodding point. your proposed sink connection, could be classed as a grey water connection, for which there is no rodding eye requirement therefore just connect between North elevation RW pipe and the new RP. One thing that should be stressed here though is - do comply with the disposal methods of solvents and acid/alkalies etc. down the sink, it's all to easy to forget when it's a garage ...pinenot

 

[damanpunk]

Ok I had dyno-rod round earlier clearing the drainpipe on the west side of the house so I did a bit of investigation.

The base of that drain pipe appears to go into a trapped gulley. It doesn't join the rest of the drain system at the rear of the house like I expected. When I run the hose through it you can see the water beneath the manhole cover and rodding point.

On the east side of the house the hose pipe discharge was visible in the same places so it's definitely a combined system. This drainpipe isn't a trapped gulley though as you can see it's dry at the base.

With that in mind should the bases of my pipes be going into sealed trapped gulleys to prevent any smells rising?

 

[pinenot]

You say the west side of the house, but your showing nothing on the drawing on the west elevation other than the garage RW downpipe, could you show me on the drawing?
By the way, your soil stackvent (also called a stench pipe in Scotland) is where both pressure and smell goes up beyond window vent intake level. Any connection made to the sewer below this should have it's safeguards, although BC would probably question that...pinenot

 

[damanpunk]

Will update sketch tomorrow at my cad machine. Basically my existing layout is wrong, I thought it travelled along the back wall of the house and tied into the east drain pipe. It doesn't, it ties in downstream of here so I think the drainage must run underneath the house or it travels south then east, sort of like how your recommended layout looks.