How to adjust slope of gutter?

[PhoenixClose1]

So I had my fascia replaced recently and the gutter reinstalled. Sadly, rainwater in pools in the middle of the gutter (about 1.5cm of water at its deepest). 

The length of the gutter is about 9m.  The difference in slope between the leftmost end of the gutter and the rightmost (where the downpipe is) is about 30mm.  Both the left and right ends of the gutter (about 500cm each side) have no water which means there is some sag in between them.

I am asking the tradie to come back and readjust but meanwhile (because sometimes tradies disappear...) I was researching whether in the worst case I can do the adjustment as easy as possible. 

The bracket style is like this (maybe exactly this):https://www.bunnings.com.au/colorbond-115mm-quad-gutter-external-bracket-classic-cream_p4790522

I understand the gutter just sits on top of this type of bracket and can be easily lifted. (One or two screws hold the gutter flat against the fascia, but there are not screwed through the gutter).

I want to avoid having to remove the entire gutter to reposition the appropriate brackets, so I was wondering if this approach can work:

- Slightly lift a portion of the gutter, to make space between it and the bracket underneath that portion.

- Put some kind of plate between the gutter and the bracket (something between 0.5cm to 1cm).

- Let the gutter rest on the bracket again, but now the gutter will be sitting on top of that thing I placed, so that portion of the gutter is slightly higher than it was.  Something like a booster seat for the gutter.

It feels like it should work, but what kind of thing should I place? And I notice the side of the bracket attached to the fascia is not straight but has an inward angle so I wonder if that will prevent the gutter from sitting properly if I put something too thick.

Thanks

[MitchellMc]

Hi @PhoenixClose1,

According to the NCC (National Construction Code), the required fall is 1:500. That would be a drop of 18mm over your nine metres.

Your method sounds like it could work as a temporary solution, and you could consider using plastic packing shims to do the job. You might find that the gutter strap tongue that gets bent over the front face is no longer able to wrap over due to the height difference.

Please let me know if you have any questions.

Mitchell

[Noyade]

Certainly a worthy experiment to try @PhoenixClose1 

I would be interested to see what happens.

But based on what @MitchellMc has explained with gradients - I get the impression with your gutter, by propping up the middle you'll increase drainage on one side, but worsen the pooling on the other side?

To me, all the brackets (minus the starting one) will need to be adjusted. For that - the gutter will have to be removed.

Also interested to see what the tradie says/does.

Cheers.

[PhoenixClose1]

Thanks @MitchellMc @Noyade 

Yes I was thinking of plastic shims. First heard about them from some people who were talking about jacking and packing their stumps.

Anyway I tried doing what I was thinking about. I'm 100% confident it can work.

Unfortunately in my case the leftmost part of the gutter is already touching the roof sheet so it cannot be lifted up further.

Only possible solutions are:

- prop up the middle part using plastic shims such that there is no sag. Hopefully the slope is enough to flow the water in the right direction, however slow. 

- The proper way: take off the gutter and reposition the brackets, most likely also shortening the downpipe a little. Something beyond me at this time.

[PhoenixClose1]

"A better slope would be 10mm per metre, so a 90mm drop over the full length."

That would have been nice. I keep wondering why plumbers are so stingy about slope. It's free!

[MitchellMc]

Sorry, a bit of an edit @PhoenixClose1. I do see that according to the NCC (National Construction Code) the required fall is 1:500. Which is far less than what I had previously stated. That would be a drop of 18mm over your nine metres. 

So, in your case, it's not that the slope was not adequate; it's just this sunken part in the middle.

Mitchell