In article ,
****gums writes:
Hi all.

I've got a question about harvesting our garage roof rain water.
Please excuse the long and rambling description.

I've got a simple downpipe from one side of the roof, which passes
by the water butt and has one of the short horizontal tubes to catch
water flowing down the inside surface of the downpipe, until the
water butt is full.

There are a couple of niggly issues with it.

1. In a real downpour, the adaptor in the downpipe adds too much resistance
and water spews out of the downpipe where it shouldn't, and runs all down
the wall and all over the outside mains socket (although it's not got
inside it yet, and it's on a 10mA RCD which should quickly notice if it
does).

2. I don't use the water in the butt very fast. It can stay there a long
time.

If I was doing this again, I would consider routing all the rainwater
into the butt, and have the butt overflow into the soakaway/drain.
That would change the water more frequently, although it's never
gone stagnent, even through long hot periods. It would also remove
the effective flow restriction from the downpipe. However, it would
result in much more water passing through the butt, which would
become more of a settling filter, and build up sediment much more
quickly. At the moment, mine has very little sediment in the bottom
even after what must be 7 years since I cleaned it out (which wasn't
necessary even then, but as the tap broke and it had to be emptied
anyway...) The inlet does have a filter though, which wouldn't be
so practical if all the water went through it. I have got a mental
design for a better inlet/filter combination, but it's so far down
the todo list, that it's never going to get done.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]