Have sealed the hole in the cast iron pipe but I’m now wondering if there is a potential build up of organic stuff – mud most likely.

What can I pour down the pipe to clear the blockage or reduce it?

Ideally not something that’ll be toxic to whatever water treatment system the water drains to.

Thanks.

Could you push a hose pipe up whilst on spray?

Pipe is the downpipe from roof gutter and it then goes into the ground through a sealed grate.

Pipe is the downpipe from roof gutter and it then goes into the ground through a sealed grate.

Ah!! Dunno then tbh.

That’s tricky if it’s sealed at the bottom.
Is the downpipe straight down to the drain from the gutter or are there bends?

I’d check the gutter/downpipe junction first.
If not that then I’m not sure what you do.

Do you have a tiled roof with red , granular sand on the roof tiles?
Chances are these have , over time washed down into your down pipe and filled it up
Do you have soakaway or surface water drainage?
If it is a soakaway you may be able to dig down and find the opening of the clay pipe and flush it out
Or Karcher do a snake pipe cleaner which will eventually make a hole
You may be better off droping the downpipe off the building and drawing the crud backwards toward you to clean as much as you can, using all mammer of spoons , trowels etc
If its a surface drai it should be roddable and running a garden hose up it should clear it

House was built in 1870, gutter and downpipe in place since then. Gutter to downpipe has a collector thing at top, but just below that had a hole – I’ve sealed that but whilst doing some clearing of the gutter, some of the mud went down downpipe…sounded like a small pool of water at bottom of pipe but that is under the ground. Pipe is hard against the wall and is solid.

Small pool could be a trapped bend older systems often were combined is there a manhole nearby try from that point with hose up each line see what happens . Bigger job but Poss cut out a section of down pipe to fit a rodding eye for future use

Had similar a few weeks ago, gutter empty but down pipe over flowing, found a tennis ball in down pipe,
Feed a hose pipe into hopper and turn on and try and flush crap through

150 years of leaf litter tends to get a bit blocky at times. Where does it drain to is the first and foremost question.

Tried a drain rod – claw didn’t fit but rod did so gave a Wiggle and felt a tweak then a water noise. Pipe then not full of water but empties a watering can into it to see if it was clear – it isn’t but has a plastic looking thing floating in it (which I can’t remove…cant get my hand past gutter downpipe piece. Will try to get claw in again and hopefully loosen more stuff…

Tempted to pour some sink plug unblocked in there and see if that helps!

You’ll probably find that its ****.

Ours has an access hatch just above ground level.
A month after we bought the house I realised the downpipe was blocked.
I used a bendy bit of hazel – the blockage was about 1metre of leaves and concrete tile grit, all a few cm above the inspection hatch. It must have never been cleared since the gutters were fitted..
Once it goes, it goes spectacularly.
Can you fit an inspection hatch into the downpipe?

Doubtful…I have issues not sticking my hands together trying to get a strip of sellotape!