Leave drain open?

[asalcedo]

A 100 square meter flat roof of a house in Spain drains into a drain located at the centre of the roof.

The drain itself is a good quality German PVC type, with a removable radial grill at the top with a semi sphere cup at the bottom. The semi sphere cup fits into the circular siphon type hole attached to a 110mm PVC drain pipe.

The problem is that the other day, during heavy rain, the drain got clogged with pine needles and muddy dirt. Most of the roof got flooded with several inches of water. After cleaning the drain all was well, but, I caught it early. A few hours later and I wonder if the roof would have held. The water would have been much higher.

Since the house is going to be empty during the rainy months, and although there should be a caretaker visiting on a regular basis, I wonder if it is better to leave the drain open, without the grill. This way, almost the full 110mm diameter of the PVC drain pipe would be open and exposed.

Is there a risk that the PVC pipe will get clogged? A clogged drain pipe is a much worse event than a clogged drain. The drain can be cleaned quickly, but the drain pipe is long and twisted and I assume it would be quite difficult to unclog.

There are some pine trees and other vegetation nearby which means that there will always be some debris on the roof that will have to go down the drain.

Thanks,

Antonio

[Bob Minchin]

Depends where the water ends up. If it goes into a public drain then this is likely to be able to cope with the debris and if the pipe were to block it could be power flushed.

If the water goes to a soakaway then the debris will eventually block this and it will be a big digging job to make a new soakaway.

Bob

[Owain]

On Oct 16, 7:43=A0pm, asalcedo wrote: ...

Is there not an overflow spout on the parapet wall in case the drain blocks?

Owain

[Invisible Man]

How about a convex grill over the top of the existing radial grill. If the lower part 0f the convex grill got blocked any build up of water would go over the top of the top of the blockage.

[george [dicegeorge]]

or make an overflow gap which would come into play when there's an inch of water on the roof - angle grinder!

[g]

[asalcedo]

To open a few holes on the parapet wall is a partial solution.

At the moment the parapet wall is about 35cm tall and does have an opening at roof level for a door.

The problem is that the roof is large, the door > ;2516974']> ...-

[Tabby]

Better to make a long cone shaped filter. The more the debris capacity, the longer it'll work until it clogs.

NT

[Invisible Man]

I meant a filter with the convex facing upwards so hopefully the debris stays on the roof well spread out until it is cleared.