Use a rope as a siphon?

[Etaoin Shrdlu]

Mum and Dad have a small pool of water on their long flat garage roof. I thought it might help to put a piece of rope I had (sisal) up there, and dangle it over the edge, in the hope that it would draw the water off. But it isn't - in fact, if anything, the rope seems waterproof. Should this work? Is there a particular type of rope that would be better? I imagine that skipping rope would work better, but I don't even know what type of rope you'd call that.

[Tim+]

Maybe its treated with something water repellant as a preservative? Wouldn't harm to try some washing up liquid on it surely?

[dennis]

capillary matting.

[newshound]

But it isn't, strictly, a syphon. The only benefit from dangling it over the edge is perhaps to provide some stability, and some extra area. IMHO it might be more effective to provide an area of mat somewhat larger than the pool.

[Tim Streater]

Not sure what the OP is expecting to happen. If the water gets drawn up into the rope, it'll just evaporate.

[Etaoin Shrdlu]

I don't think I explained very well. I want to place it horizontally, and sort of draw the water along it, not up. I imagine that having some hanging over the edge will make it more likely to drip away, like wet clothes on a line. Of course, the rope has to get wet first.

[Etaoin Shrdlu]

Yes, it is so water repellant, that I think it must be treated. I'll cut a bit off, and try washing-up liquid, and see if that makes it more absorbent.

[Tim Lamb]

This reminded me of the technique used to produce acetylene and the time interval for early versions of agricultural bird scarers.

Basically a thread wicking water from a reservoir to drip onto carbide in a pressure vessel. More threads = more bangs per hour. Rural dwellers may recall these ran all night.

I think most modern rope will be made from some form of plastic. Polyester etc. I suppose skipping rope could be made from cotton...

[Brian-Gaff]

This is capillary not a siphon, surely? The same idea used in greenhouses between trays to take the water along and even up in some cases. You need something absorbent for that. I somehow think that the actual speed of such an idea might when be overwhelmed by the average rain shower, unless you find a very big bit of capillary matting. Unfortunately, this will have the side effect of moving the damp all over the path of the matting. Brian

[Brian-Gaff]

Yes but the growth of all sorts of things on it would render it very short lived and as isaid in another reply, it would in fact spread the water to other places to help it leak through. A large sponge in the puddle might evaporate it faster if you attach a rope to it and just use it after the puddle has formed and remove it afterwards.

My feeling on this is that if its not actually penetrating the roof, leave well alone. Certainly do not walk on it. Brian

[mark.bluemel]

Possibly not. I'm sure I read somewhere that natural fibres are kinder on bare skin. Ahem.

[Etaoin Shrdlu]

The roof is well sealed. Unfortunately, there is a window overlooking it, and my mum has got a bit obsessed with it.

[Etaoin Shrdlu]

I'm not sure what the word would be. Someone else used the word 'wick' and that seems about right. I'm going to try cotton rope, now that I know it exists.

I'm not too bothered, as long as it clears it eventually. To keep my mum quiet. Until she finds something else to worry about :-)

[Tim Lamb]

How about dressing the roof with stone chip? Hide/disperse the water and improve fire resistance...

[Etaoin Shrdlu]

Good idea. It has been covered with chippings in the past, many of which tended to end up in the drain at the rear, eventually blocking it. Perhaps there's a way of keeping them up there, like some sort of mesh?

[GMM]

Not sure if it will help your plan much, but isn't sash cord made of cotton? That might soak up water.

[Etaoin Shrdlu]

I've had a look on ebay, and cotton rope appears often to be described as 'sash' cord. Quite a lot of it appears to be associated with bondage, which is something of an eye-opener. I need to get out more.

[Tim Lamb]

In message , Tim Streater writes

Mebbe glue the ones next to the gutter drip with a thin layer of roofing mastic?

>

[mark.bluemel]

When I've replaced sash cords in the past, I seem to recall the cord being a cotton outer sleeve round something else - perhaps hemp? A quick google suggests cotton round polypropylene is common now.

I refer the honourable member to my previous remarks.

Or possibly stay in more, depending on what you get up to while you're staying in :-)

[Etaoin Shrdlu]

Oh yes, I'd spotted that one :-)

Well, there is now a jiffy bag full of rope on its way here. I'll try not to get carried away.