Replacing a downpipe:
Begin up the ladder with two 95-degree elbows. And hold the first elbow off the wall the distance the brackets will hold the downpipe off the wall. With the second elbow over the top of the dropper outlet from the spouting. Measure the straight pipe required between the two elbow sockets. Cut this section of pipe and go back up the ladder and have a dry run at fitting this offset. When it is ok. Use the manufacturers solvent cement and glue these two elbows together and then place dry on remaining length of downpipe.
Lifting the downpipe way up in the air and guiding it onto the spouting outlet dropper mark where the downpipe reaches to and if it is already reaching the drain and hitting the ground take the downpipe down again and remove the offset and getting back up the ladder make a mark where the socket inside is on the wall. Measure from this mark down into the drain adaptor by 2-inches (50 mm) and make this cut and try to fit the downpipe again.
If you can get it to fit take the downpipe out for the last time and glue the offset on at the top and then replace downpipe in position and fit the downpipe clips one per yard (1 per metre).
If you have trouble getting the down pipe up in the air on the dropper and into the drain mark where the downpipe crosses the drain adaptor and cut to this mark and try again and again this way until you manage to fit the downpipe correctly. If this downpipe is going to be a charged system you will need to glue the positions where the adaptor goes into the drain and where the downpipe goes into the adaptor.