Not sure how to describe it but . . .

[Dave Liquorice]

Or through the drains. Downstairs loo? Floor drain in the scullary?

TBH fixing to the door frame seems a bit pointless to me. The water will just find it's way between the frame and the wall. Don't think a tiny bead of five year old silicon is going to keep it out...

Bits if ali U channel on the outside faces of the wall, solidy fixed and witha full layer of sealant behind. Don't forget the horizontal at the bottom of the opening. The board that slide down into this needs a compliant seal of somesort arranged such that the weight of water compresses it even harder. If there is a joint between boarsd that will need a compliant seal as well and again idealy one where the weight of water makes it seal harder. Not sure how one would arrange that.

Also see what your insurance company has to say about DIY flood gates. In my view they should support you, as you are trying to reduce the losses but knowing insurance comapnies if you don't use "approved" kit they'll use it as hook to hang not paying out on.

[Dave Liquorice]

Might depends how much higher up the water is getting into the drains. Remeber that hefty great cast iron road strength manhole covers can be tossed aside by flooded drains... See artesian wells, same principle.

You can get one way valves to fit into the waste pipe to reduce the backflow.

random examples from the first page of google "drain backflow valve".

[Nightjar]

Which is why I was thinking of an open topped pipe, rather than trying to seal the drain. I take your point about how much higher the water is getting into the drains, but in my house the foul water drain is connected to an open gulley outside the kitchen, so it wouldn't rise in the pipe any higher than the water outside.

Colin Bignell

[Bob Eager]

The stress of the impending flood will probably provide sufficient material to do that.

But yes, it's where you see a lot of the nastier stuff come in.

[Grimly Curmudgeon]

I saw a diy floodgate on a door recently, made from U-channels bolted to the frame, down which slotted a few horizontal 6x2 timbers. It would have been trivial to make the gate in one piece, but I suspect the piecemeal approach was to keep the weight of each part low, in case the bloke wasn't available and his wife or kids had to do it. I unrecall the method of tightening them down, but it wouldn't be difficult to rawlbolt in a tie-down and fasten a ratchet strap. Inside the door, under a grating, was a sump with a pump in it.

Of course, all this is for nought if the water simply comes in the underfloor vents, or up through the floor or toilets, so pay attention to that too.

[Apellation Controlee]

------------8><

Presumably the pump was a manual one - or did he have his own generator?

[fred]

Yes, that works when there's an equalised static pressure and the water has found its own level. Consider also the state where moving water has found its way into the drains and is under high dynamic pressure that would find it jetting above the level of the pipe and potentially disrupting the fit and seal.

To cope with those situations, I'd be looking at reverse flow prevention devices _plus_ the precautions you advise.

[fred]

Considering the consequences of failure, it's got to be mechanical fixing plus glue.

[Grimly Curmudgeon]

I only saw an electric one in place, but it would have been trivial to drop a manual one in. When it floods there, the power supply is intact. The house has a history of flooding, being at the foot of a hill and dodgy rainwater drains in the road unable to carry it all away, so the owner was driven to take measures.

[Apellation Controlee]

I was thinking only that loss of grid power is often a consequence of area flooding.

[Grimly Curmudgeon]

That particular house suffered from a more localised problem, though. Quite a decent house, apart from that once-every-few-years little problem