More help on External overflow on cistern

[DIY-JC]

Back again.
I had some great help with my last post "Adapting Well Bottom cistern flush, not replacing" but I could do with a little more help ( thought it rude to bump an old thread so here's a new one).
The overflow from the cistern is 15mm running just off horizontal out of the back wall.
Last week the Torbek Valve failed and water came in faster than the overflow could deal with it. I had taken Hugh Jaleaks advise and slowed the water down so the overflow could cope with the speed but at some point it must have been fully opened so you can guess the outcome.
I am going to re-plumb the cistern and fit a ball valve.
My question is
If I have the overflow run vertically down from the cistern then 90deg out of the wall, would that work? Or would running the pipe at 45deg straight out of the wall be better?

 

[oldbuffer]

1. Vertical then out would be OK.
2. Overflow pipe should be of larger diameter than inlet. Its normally 21.5mm plastic.
3. If you can't use larger pipe (I haven't read your original posting) you could use a flow limiting isolation valve such as BES item 17527. Note that you have to buy the insert separately. If you used a 8 litre/minute insert, the WC should still refill in just over a minute (assuming a 2 gallon cistern)

 

[DIY-JC]

Cheers for the quick response oldbuffer.
Its 15mm outlet pipe coming off the side of the cistern. Thats the biggest I could get to fit.
Down then out would be easier than having to drill 45deg through wall!
Looks like I'll also be adding a Flow limiting Isolation valve for belt and braces!.
That's my weekend booked up. Wish me luck.

 

[Hugh Jaleak]

Just fit a quarter turn valve to the supply, such as https://www.screwfix.com/p/flomasta-full-bore-isolating-valve-15mm/46860 and close it down enough to reduce flow into the cistern.

Cant remember what we said previously, but if you can control the flow coming in to something the overflow can cope with, should the Ball Valve fail completely, then the overflow can cope.


If this is an old cast Bell type cistern, then the original overflow would probably have been Lead.

 

[foxhole]

Change internals for an internal overflow to loo . Simpler and will easily cope with water rate .

 

[Hugh Jaleak]

Change internals for an internal overflow to loo . Simpler and will easily cope with water rate .

I think the OP has an antique Bell type cast iron cistern, on a High Level flush. Changing the internals isn't really an option.

 

[DIY-JC]

Change internals for an internal overflow to loo . Simpler and will easily cope with water rate .

Cheers Foxhole. I would love to do that and I've found a website of someone who has done it. Let's just say I've been told no.

 

[DIY-JC]

Thank you everyone for all your help.
I'm going for flow regulating ball valve on the outside at high level. New float valve on the inside.
Overflow will be 15mm coming out of the side then a vertical drop of 1m before going out of the wall. If it still can't cope, I can drop the flow with a smaller cartridge or just turn the valve at high level so it cant be messed with.

BUT
I have read that 15mm overflow is a total no-no because it will be overwhelmed and overflow.
If I can get 21.5mm overflow through the hole, would I be able to go out the side, 90deg elbow and through the back wall of the bathroom?

 

[Hugh Jaleak]

If I can get 21.5mm overflow through the hole, would I be able to go out the side, 90deg elbow and through the back wall of the bathroom?

Hole in the Cistern? If you can use 21.5mm pipe then that's the correct stuff for the job. Its rare a Ballvalve fails on full bore anyway, they usually give some warning they're on the way out.

 

[DIY-JC]

Sorry, the hole where the outlet goes through. I'm assuming if I can get 21.5mm through then having a vertical drop wouldn't be as necessary.

 

[DIY-JC]

Final one.
Had a go with 21.5mm overflow and it won't fit through either holes. Guessing it was made for lead as Hugh Jaleak said. I had the cistern in the garden over the weekend and ran a couple of tests. I got the 15mm overflow to syphon with a 1m drop before going horizontal but the water was virtually level with the hole where the chain arm hinges on the body before it happend. The water didn't go down but also, it didn't get deeper - but the inlet was at full bore though, not fitted with the flow reducer.
That is the best I can get so I'll go with it and reduce the flow to a trickle.