cast-iron downpipe to plastic

[foy9999]

Ok so I think I've found a solution, using plastic downpipe I had lying around....

The pics will show better than words but basically I had some (probably) obsolete downpipe that is a smaller OD then the normal 69mm stuff you get everywhere.

The old stuff fits quite easily into the standard stuff so I hoped it would slide into the cast and could be bonded somehow to the plastic downpipe. Acting like a spigot basically.

Turns out it was too wide to fit in the cast so I slit it then removed a strip and due to its natural spring it is a tight fit in the cast.

Next thing to do was put the downpipe over it but obviously it's no longer a snug fit in the downpipe (as its OD has been reduced).

I therefore cut another bit of it to act as a collar. That fits over the slit part (inner sleeve) and reduces the gap between the sleeve and the downpipe.

I then puttied the gaps between the 3 parts.

So water now comes down the downpipe and over the putty on top of the collar and sleeve.

It might be better if the parts were all bonded together in the downpipe so it could just be lifted in and out of the cast but it seems to be working fine (was raining today and no drips).

The only downside is that the old, badly-cut (smashed?) part of cast is now visible at bottom of pipe. This was previously covered by an upside-down pipe-socket.

If the customer is bothered by it will need to paint it black. If they are really bothered by it will need to remove everything, cut the cast just below ground-level, buy new downpipe and make the connection again

We shall see....

previous artisans left this showing when installing plastic drainpipe

it was covered by (straight) pipe-socket allowing water to drip out

correct end of (straight) pipe-socket does not fit into cast pipe

standard downpipe will not fit over cast

possible solution using narrower downpipe inside 68mm to act as sleeve/spigot

narrower downpipe also too wide to fit inside cast

overlap needed removed

new sleeve is tight fit in cast

yellow area and between pink and blue have been packed with putty

 

[foy9999]

You can buy cast to plastic adaptors, problem is the myth that everything was better in the old days. Cast down pipe is often not "standard" sized or particularly round.

If it's hidden use the rubber one, if not CT1 is the answer

Not really sure what you mean about the myth but I can't find any adapters for connecting 68mm downpipe to cast iron (2.5" OD) downpipe, hence the thread.

You can get adapters to joining cast-iron guttering to plastic guttering but never seen any for downpipe.

 

[gaz1]

pull it back out and glue it all up

putty will fail its why we dont use it on the toilets for the same reason its only a filler and it goes hard on a toilet pot

you dont see them because there normally replaced with either plastic or cast downpipes

 

[foy9999]

I think this is it (plain end loose socket), but they do not give any dimensions of the small end. From the description, it says it is to connect two plain-ended pipes.

Cast Iron Round Downpipe Eared Loose Socket with Spigot - 65mm Black

Cast Iron Round Downpipe Eared Loose Socket with Spigot - 65mm Black

www.guttersupplies.co.uk

Yes that would definitely work connecting 2 cast-iron pipes and, as the OD of plastic and cast is similar, am sure you could squeeze plastic downpipe into the upper part so it would work in my situation but would mb look a bit odd at bottom of pipe

 

[foy9999]

pull it back out and glue it all up

putty will fail its why we dont use it on the toilets for the same reason its only a filler and it goes hard on a toilet pot

you dont see them because there normally replaced with either plastic or cast downpipes

Not sure I agree with that. I come across this problem a lot - ie on all ex-council houses in my town where the cast has been replaced with plastic - and they never replace the bit under ground with plastic or put new cast on.

What exactly do you mean by pull it back out and glue it all up? Sounds like a bodge

I use putty all the time. Never have problems with it. It's actually Plumbers Mait but same idea

 

[Mikes]

Since there is block paving around the cast iron, I would be inclined to lift a few bits and see if the iron goes into a salt glazed or similar pipe in the ground. If so, remove the iron and put the plastic straight into the pipe. Looks a right old mess that the council contractor left.

 

[Beeezer]

Give it a bit of this…

 

[gaz1]

Not sure I agree with that. I come across this problem a lot - ie on all ex-council houses in my town where the cast has been replaced with plastic - and they never replace the bit under ground with plastic or put new cast on.

What exactly do you mean by pull it back out and glue it all up? Sounds like a bodge

I use putty all the time. Never have problems with it. It's actually Plumbers Mait but same idea

ours goes into a glazed fitting close to the surface so is just as good to fit a new downpipe wether cast or plastic note ours also goes through stone often

scotland does have an interesting cast pipe as i took notice of it while i was up there

so whilst you might class it as a bodge its a bodge from the start gluing up the tube or what you could have done is sloped it and glue it

lead would have been easier to create and make up just from a square piece

putty or plumbers mate goes hard always has done and will fail over time

we used to use it on the rear fittings on toilets for the toilet box flushpipe with rope to create a seal nowadays its a rubber bush simple yet does the job yet fails sometimes

 

[Onoff]

You want something like this but I presume this is the wrong way round:

BES.co.uk | Next Day Delivery On 15,000 + Plumbing Supplies

Order Rainwater Systems / Pipe Connector - plus Gas and Plumbing Supplies online at BES.co.uk. Low Prices, Free Next Day Delivery Available, 15k Plus Products in stock P/N: 12311

www.bes.co.uk

In the Q&As someone asks a question about sizes, the seller answers thus:

"The top of the fitting has an outside diameter of 89 mm and an internal diameter of 82 mm. The bottom opening has an outside diameter of 64 mm and an internal diameter of 59 mm. Basically the cast drops into the top and the bottom drops into the down pipe".

Or this but I can't find dimns:

Polypipe 68mm Round Downpipe to Cast Iron Adaptor Black

Polypipe RR131B 68mm Round Downpipe to Cast Iron Adaptor Black

mjplastics.co.uk

Find a decent plumbers merchant who has one in and get them to measure it.

As I say, 3D printing is always an option.

 

[Kayos]

Not really sure what you mean about the myth but I can't find any adapters for connecting 68mm downpipe to cast iron (2.5" OD) downpipe, hence the thread.

You can get adapters to joining cast-iron guttering to plastic guttering but never seen any for downpipe.

The adaptors exist, the myth is that the cast pipe is the correct size throughout its length or indeed particularly round. Never found old cast fall pipe that is in many years. Easiest option is to replace the full length