Running shower waste to rainwater downpipe on combined drainage

[cr0ft]

Hi all. For cosmetic reasons I would like to run a 50mm shower waste pipe directly into a 68mm rainwater downpipe at first floor level. There is a stack on the opposite side to the downpipe but it will look messy running the shower waste pipe around the drainpipe to meet it. Moving the downpipe is not an option.

The drainage at the property is combined and the downpipe flows into a gully and into 110mm PVC drainage pipe underground. Is there any reason why I can't do this? I know that conventionally they run into soil pipes directly but logically with a combined system I can't see anything wrong with doing this. The downpipe vents at the gutter (obviously) and is high enough above the upstairs windows to avoid smells coming back in.

Also, does anyone know where I can get a 50mm to 68mm boss connection for this?

 

[Nostrum]

If the down pipe blocks you'll get wet.

Can you not drop the waste into the gully?

 

[cr0ft]

Fair point but have you ever seen a downpipe block anywhere other than the hopper on the gutter? The same is true for a soil pipe blockage too isn't it?

It's on the front of the building as that's the only way we can get the shower waste out (joists are only 4" or so and in the direction I want to run the waste). It's also right on the limit of pipe run even for 50mm pipe.

Sorry I wasn't clear, the downpipe drains into a drainage p-trap rather than a gully.

 

[cr0ft]

I meant to add, the reason I don't want to run it down by the downpipe in 50mm is for cosmetic reasons, I want as little pipe on show at the front of the building as possible really, I would prefer to run it around the downpipe and to the soil stack on the side of the building in preference really.

 

[Nostrum]

It's quite common for down pipes to block underground mate, the rain washes all the crap off the roof. Seen boilers flood because of it. Difference with a drain blocking is you can turn the taps off, if it's raining hard it just keeps coming and you are funnelling all the rain off the roof in that direction.

I take it the 50mm is coming out of the wall to low to kick the down pipe over it to get the 50mm in behind?

 

[tom609]

There aint a problem providing it is foul drainage (1 pipe drainage system)

 

[Nostrum]

I don't do bathrooms so not familiar with the products but don't they make pumps for wet room shower traps? Could you use one of these and reduce the pipe size if it would help?

 

[Ray Stafford]

Also, does anyone know where I can get a 50mm to 68mm boss connection for this?

Never seen one.

Whenever I have seen this done, it has always been into a hopper, or on larger systems which use 4" or 6" soil as downpipe.

 

[cr0ft]

Fair point re rain being something you can't switch off and not worth the risk really! I could kick the downpipe over it or run the 50mm waste around using 2x offsets formed with 135 bends. Means the waste pipe run is going to be closer to 5m though whichever way I do it but still infinitely preferable to a pumped solution in my opinion. A standard shower pumping out around 9 LPM isn't going to come close to plugging a 50mm waste pipe so I don't think self-siphonage will be an issue.

 

[tom609]

Why bother with a pump just run it into the hopper head if there isnt a hopper head already there fit one

 

[cr0ft]

I don't do bathrooms so not familiar with the products but don't they make pumps for wet room shower traps? Could you use one of these and reduce the pipe size if it would help?

Really want to avoid any pumped solution. After having nightmares with a Sanishower install at the moment I don't want that stress every again!!

 

[cr0ft]

Why bother with a pump just run it into the hopper head if there isnt a hopper head already there fit one

I thought you weren't allowed to fit these for waste pipes any more?

 

[tom609]

Of course you can

 

[Ray Stafford]

I wonder whether a rubber boss adaptor would fit in an RR129 down-pipe junction?

 

[cr0ft]

Reg 1.7 of Part H,

Branch pipes should discharge into another branch pipe or a discharge stack unless the appliances discharge to a gully. Gullies are generally at ground floor level, but may be at basement level. Branch pipes should not discharge into open hoppers.

But then I can't have a 50mm pipe run longer than 4m according to the regs either!!

 

[tom609]

Rainwater head!!!

 

[cr0ft]

I wonder whether a rubber boss adaptor would fit in an RR129 down-pipe junction?

I'm going to avoid direct connecting it in for the reason mentioned already, if the downpipe blocks below first floor level that will be one hell of a flood into the bathroom.

My options are either a 5m long 50mm pipe run for the shower or discharging it into a hopper, both of which seem to be prohibited under the approved document H.

 

[Ray Stafford]

or discharging it into a hopper, both of which seem to be prohibited under the approved document H.

Despite being the solution on several million houses nationwide! 🙂

 

[cr0ft]

Despite being the solution on several million houses nationwide! 🙂

Yes I agree. I think I am going to go with a hopper as it will look the neatest. This one is going to be a case of sticking 2 fingers up to the approved document. It's not a legal requirement after all!

 

[Nostrum]

Thought it was ground floor for some reason, what's the reason for not allowing it to drop into a hopper, that's stupid?