Rainwater Downpipe - Direct connection into shared sewer

[VDubDan]

As part of doing an extension, I'm going to take the advantage at cleaning up my existing drainage connections. I have a 30's house with a combined sewer system - I currently have a rainwater downpipe (which also picks up the bathroom greywater) that discharges into a very old school concrete gully. The kitchen and utility greywater also discharge into the same gully.

It's not very pretty - it's basically been built up with breezeblocks and everything just terminates there.

My questions: When I tidy this up, do I HAVE to have a gully?

I've read a few things that say building regs enforce it, but approved doc H says it needs to go into a TRAP. So does an underground trap exist that isn't a gully?

My reason is purely aesthetic and I'd just like to avoid putting a gully in if such a thing exists.

 

[Ian H]

There are some manifold things that would take a few pipes but really you want a gully.

They are accessible so you can get out any ****e that collects in it, they stop the sewer smells, and they can give you a direct access to the drain for jetting and cctv.

 

[Hugh Jaleak]

Depends what you've already got to be honest. If the bathroom stack is plastic, I'd look at routing bath and basin wastes directly to that, and get shot of the existing arrangement, (which I assume is a hopper if the rainwater is going into it). (If you're not sure, stick a pic up, and we can tell you more.)

Kitchen wastes can be directly connected to the drain if you prefer, but you'll still need a gulley for the rainwater connection. This can be done via a back inlet, which can make it look tidier, and avoids moss/leaves/other debris blocking the grid, but allows you to remove detritus as required. New bottle gulley can easily be positioned to sit flush with finished ground level, all you will see is the grid.

 

[VDubDan]

That's fair, if it's gotta have a gully then it shall have one! Here's what I'm working with:

https://imgur.com/a/PtPLrL0

Teaching people to suck eggs, but for the avoidance of doubt - the furthest black downpipe is the SVT. The nearest is the rainwater downpipe, with the 40mm white bit into the hopper being from the bath and sink.

And then at the bottom, only the 40mm white waste pipe is in use now. What's not visible is that there's another 40mm waste into the left side of the blockwork - it goes underneath the slabs/steps.

I know it's not horrendous or anything, but we have some nice plans for a patio etc so now's the time.

Like the idea/look of the back inlet gully - that seems to be a nice compromise. And I think put the downpipe on its own and reroute the kitchen and utility separately directly.

 

[Hugh Jaleak]

Given the spacing of the pipework, I would be half tempted to put 2 gullies in, providing the existing drain will allow. Put one under existing downpipe, taking bathroom and rainwater, connect downpipe into back inlet, and waste coming under step via a boss. Use a riser if necessary to get the required depth on the gulley with grid at finished floor level. Then put a second in further to the right for the kitchen sink, and join with a Y onto the existing drain. Bottle gullies are roddable so there's no issues with access to the outgoing pipework.

Sadly, the stack is cast, connecting into that isn't for the faint hearted, so unless you're planning to replace it, leave well alone. (Although might be prudent to ascertain its condition before laying the new patio, if it is going to need replacing in the near future, now would be the time to do it.)

 

[VDubDan]

Given the spacing of the pipework, I would be half tempted to put 2 gullies in, providing the existing drain will allow. Put one under existing downpipe, taking bathroom and rainwater, connect downpipe into back inlet, and waste coming under step via a boss. Use a riser if necessary to get the required depth on the gulley with grid at finished floor level. Then put a second in further to the right for the kitchen sink, and join with a Y onto the existing drain. Bottle gullies are roddable so there's no issues with access to the outgoing pipework.

Sadly, the stack is cast, connecting into that isn't for the faint hearted, so unless you're planning to replace it, leave well alone. (Although might be prudent to ascertain its condition before laying the new patio, if it is going to need replacing in the near future, now would be the time to do it.)

Thanks Hugh - just out of curiosity, what's the benefit/advantage of putting in the sink outflow via a gully? Is it just to give easier access for rodding in future?

 

[Hugh Jaleak]

Yes, but you can connect directly to the drain if you prefer, using a boss connector. I'd just make sure the waste is accessible for cleaning if needed in future. Avoid putting fat down the sink, if a kitchen waste or gulley blocks, 90% of the time I'd say it's due to fat.