Still on with the patio drainage, decided to place linear drain around the building. Few questions I could do with clarifying though. Is it ok to replace existing gulley with a p trap connecting to liner drain. See photo attatched.
Other question is due to the length of the building I will have to cut a channel a ft. How do I join the cut channel to the corner piece and is it better to have a full length on the corner piece and put the cut piece in the middle of the run. If in the middle of the run how is te best way to join them.
You could probably do away with the gully and P trap altogether, by getting a sump (sometimes called a trash box) to match the linear drain. This will normally be half the length of a standard linear drain channel but much deeper with a removable silt basket. It should have various places on it that are formed to connect to the surface water pipe, just need careful knocking through with small chisel and hammer.
If you break out the clay gully, set the trash box in place to connect on to the linear drain, and then cut the downpipe to discharge into either the linear drain or the trash box, possibly with an elbow at the end of the downpipe. Then connect the trash box to the drain pipe, you may need a couple of bends to do this.
As for cutting channels, the one in your pic looks like all plastic...cut using abrasive wheel on an angle grinder or a handsaw. If the grating is metal use the abrasive wheel. If you can put the cut end of this channel at the end of the run, and then then the other end should couple to the end of the next full channel. To block the cut end there are manufacturers end caps....this is a fairly general idea, difficult to say more as there are so many different manufacturers, materials, joining methods etc. when using linear drains. Some manufacturers even have (If i remember rightly) a grating adaptor that will take a downpipe directly into the linear channel.
