Bathroom drainage, divert into soil stack?

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GeX

GeX

GeX

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Currently, the toilet goes into the soil stack but the sink and bath go into another drain (old (Edwardian) house, mixed drainage).

It looks like this



The problem I'd like to fix is that when a full sink / bath is drained, it ends up flooding over the hopper that the pipes mix in



I have already bought a larger hopper and a new (black) down pipe but began wonder why this wasn't just connected to the soil stack in the first place. The main stack is cast iron but from the branch is plastic.

Is the drop not enough? Is there a risk that toilet waste would back up the sink/bath pipes if they were connected?

If there's a real reason why it can't be connected to the soil stack, what's the best way to stop the bath / sink from overspilling? Just a bigger, deeper hopper, a lid?

What would OcUK do? (Apart from replace it all in black pipe and repaint the soil stack as that's getting done regardless!).

The bath waste also carries the boiler condensate, if that's an issue for a cast soil stack or not, I don't know.
 
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No reason they can't be run across into the soil stack provided you have enough drop, I'm surprised the hopper over flows as the flow rate down the pipe below should be more than enough to cope sounds like it is blocked to me, one thing you could consider doing is t'ing the two together and then putting the output of that join into a pipe that is pushed down into the down pipe so the hopper isn't involved in the process at all. Personally while you have the scaffold up I'd remove the lot including the soil stack and replace it all, the pipe off to your toilet is a mess and those two pipes going into there own hopper are nasty and ugly get it all neatly into a single stack and never worry about it again.
 
I don't think the hopper fills up and overflows, I think it's just the water flow into hitting the bottom / side and bouncing up. I looked into doing away with the hopper but due to the way drains are kept split on modern builds, there was nothing off the shelf to put a 40mm waste pipe into a 68mm rainwater pipe.

I'm not up for ripping out the soil stack and redoing that too, after having the house repointed and the roof / fascias / barge boards done I'm a bit skint!
 
GeX said:
I don't think the hopper fills up and overflows, I think it's just the water flow into hitting the bottom / side and bouncing up. I looked into doing away with the hopper but due to the way drains are kept split on modern builds, there was nothing off the shelf to put a 40mm waste pipe into a 68mm rainwater pipe.
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Is it related to the angle at which the 2 pipes hit the hopper then? Could it be solved by shortening the big pipe the hopper sits on, and then getting longer lengths of pipe to join the hopper, and they would then be at a shallower angle, i.e. top 2 pipes would be pointing down nearer to the vertical.
 
Send them in to the stack tbh. Easily done if the cast iron is replaced with plastic. Did the O/H's last year not too bad a job, if you've got cast iron coming off the branch in to the bathroom too it can be a bit of work to get it out. Cut the cast iron in to sections as it's heavy and one large piece is difficult to handle. It's also brittle too.
 
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You would be cutting a hole in the pipe and use a boss to connect the sink/bath too. The angle of the plastic pipe may be a problem. Although I think angled boss adaptors are available. You would have to rejig the bath and sink pipes into one. Could be a pain if you need to access behind bath panels or boxing in for that one pipe with the bend flush with the brickwork. They have left no play there.
 
I've got a very similar set of pipes for our back bathrooms. Last summer I made a diverter pipe that I can swap in during the hot dry summers, so that the water goes into a water butt first, before going down the drain.

The water comes from our sinks and showers - so very far from drinkable - however the grass and plants don't seem to mind.
 
Does your soil stack have a vent at the top? If the pipes are connected directly, there's a chance a 'large load' in the stack could suck the water our of your p-traps. You might want to add an air admittance valve if you do go down that route.
 
GeX said:
The stack is vented.

The hopper is not overflowing, it's splashing over from high flow hitting at that angle
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Ideal situation would be replace the bottom half with plastic. Getting it out is difficult because 4 inch cast is quite heavy. But easy to join on to with a timesaver fitting once its out. You could then get a branch with boss adapters and run the additional waste pipes into the branch.

You could use push fit 4 inch fittings they give you a bit of flexibility with solvent weld if it’s wrong you will never get it apart.
 
Personally I wouldn't bother getting involved with the stack, looks like unnecessary work/hassle. Looking at your pic I guess the easiest thing to do is fit a couple of 135 bends as already mentioned to try and direct the water into the downpipe rather than hitting the hopper. If you want to get really fussy about it put a section of 50mm pipe directly into the hopper then T those two pipes into it, seems a bit overkill though.
 
gingergundog said:
Personally I wouldn't bother getting involved with the stack, looks like unnecessary work/hassle. Looking at your pic I guess the easiest thing to do is fit a couple of 135 bends as already mentioned to try and direct the water into the downpipe rather than hitting the hopper. If you want to get really fussy about it put a section of 50mm pipe directly into the hopper then T those two pipes into it, seems a bit overkill though.
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I’m not ripping any of the cast stack out, it already has plastic branched to the toilet. If the others can be joined, great. If not they’re staying at the hopper with some angles on the end!
 
GeX said:
I’m not ripping any of the cast stack out, it already has plastic branched to the toilet. If the others can be joined, great. If not they’re staying at the hopper with some angles on the end!
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That was what I was saying with regard to your initial post, ignore the stack/plastic branch to the toilet. Just rejig it where it goes into to the hopper. Make sure you get the correct fittings though.
GeX said:
If there's a real reason why it can't be connected to the soil stack
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