Suggestions for a gutter dam

Just stick a bit of a paving block in.

I have some old Marley 160x80x30 mm blocks and they just fit inside the top of the hopper and hold back leaves but don't stop water getting either side and under.

You seem to have misunderstood my requirement. I want to stop the water so it builds up and back flows.

it needs to be either: floppy to conform to shape = polythene bag = short life or shaped to fit & with something liek soft silicone to block the imperfect fitting gaps

NT

Wonder if there are any faulty breast implants going cheap...

...had to bring it down to Adam's level somehow..:)

Plastic bags with a closure intended to keep things like soup may last longer ,you could fill one with a small mount of expanding foam so it takes the shape. Or get a small bag of quick dry cement, line your gutter with something like a plastic bag ,baking foil ,pond liner Build you dam with the cement ,you could incorporate a bit of wire coathanger to give you a dam handle. When cement is dry you have a heavy cement dam you can lift in and out, the plastic bag or foil with have stopped it sticking to the gutter and can be removed once set. Small packs of such cement are about 2kg e.g.

GH

Well I was just about to respond similarly till I saw your post.

Great minds and all that :)

Sounds a good plan - mould my own dam. Cheers.

Even with my plastic bag there's been enough backflow collected this week to fill the 200L butt and I'm in the East Mids so not that much rain. Plastic bag now removed so the water will flow down the drains.