If your polythene is "trenched" or fixed to a base rail . . .
You'll be supplied with an aluminium backing section which mounts to the leg of the polytunnel hoop on the inside of the polythene cover. The polytunnel gutter then fixes on the outside of the polythene to this backing section, with fixing screws at approximately 30cm apart.
The gutter section is an exact fit to the aluminium backing section and so the polythene cover is neatly and safely sandwiched between the two.
The gutter section is supplied in 2.2m lengths which are joined end-to-end to make the overall length a little longer than the length of the polytunnel. The gutter extends past the end of the polytunnel by about 8 inches so the rain water can run off into a water butt.
At the other end of the gutter section is a ribbed insert for the gutter stop end. And where the gutter sections join together, an aluminium foil flashing strip ensures a perfect and long-lasting seal.
Even if your cover is already fitted, it's still possible to install our aluminium gutter. You just need to carefully guide the extruded backing section bewteen the leg of the hoop and the polythene then join the sections together before fixing to the leg of each hoop.