On Wed, 12 Feb 2014 19:03:27 -0000, Janet wrote:

From childhood experience of living in a house on mains sewer services
in a flood area; one of the worst effects is sewage backing up through
toilet bowls especially in ground floor lavs.

Apart from building on land that floods being a bit daft, having a 4"
dia hole to the outside world only 18" or so above floor level seems
even dafter. Planning regs, eh?

With luck you can prevent this by plugging the U-bend . Double up some
waterproof soft plastic carrier bags and stuff them with rags, then ram
the plug down the flush hole of the toilet.

I wouldn't like to be near by when it let go... you can get one way
flood valves for the drains but to be honest most is a waste of time.
Bricks are pourus, after a week the water will just be coming through
the walls. Deeper than about 600 mm and a non-flooded building may
collapse due to the weight of water pushing on the walls, so you have
to let the water in.

Don't build in flood risk areas is the answer or if you do take
precautions like no power, no timber, no gypsum plaster less than 1 m
above the floor level. Have a plan of action, shifting everything
upstairs, backup cooking, heat and light. Trouble is these days
everyone is so used to all the services always being present most
people haven't even thought of a backup plan let alone equpiment.
More fool them IMHO likewise those that wine "we didn't know it was a
flood risk area when we bought". Didn't their solicitor check? It's
not difficult the maps are on the EA website FFS! Wouldn't insurers
refusing flood cover be a bit of a clue. Maybe not for the
clueless...

--
Cheers
Dave.