Dealing with stalled downpipes

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#3203402 5-Mar-2024 15:28

sir1963:
The "mesh" system that gets riveted onto your roof makes this impossible, sure it stops the leaves, but now what ...?

They also get larger leaves flattened against them by water pressure providing a nice smooth surface for rain to run over the top of the gutters and down the side of the house. Neighbours had this and ripped it out again after a short while.

neb

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#3203408 5-Mar-2024 15:41

djtOtago:
You could look at using 2 downpipes side by side. I have 2 pipes about 600mm apart coming off a large shed.

or look at something like
Rain Harvesting | Leaf Eater Advanced Rain Head 80/100mm White | Mitre10

Rain Harvesting | Leaf Eater Original Rain Head 90mm White | Mitre10

Rain Harvesting | Leaf Eater Commercial (Polypropylene) Rain Head 150mm White | Mitre10

Edit added another link. Rain Harvesting 80/100mm Leaf Eater Ultra Rain Head - Bunnings New Zealand

All of those except the Bunnings one have the problem I mentioned in a previous post, which is why I never considered them. I remember looking at the Leaf Eater Ultra at the time (and seeing some very staged YT videos from the US that didn't really show how well it handled debris) but didn't go with it for some reason that I can't remember.

Now that I've got some data on the failure mode of the existing setup I might ping one of the water-tank places who presumably will have experience with how it works in practice, I really only need it on the main downpipe since the backup never gets that much flow.

mdf

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#3203425 5-Mar-2024 16:39

neb: <snip> I really only need it on the main downpipe since the backup never gets that much flow.

This is probably counterintuitive, but have you tried restricting the flow on the main downpipe? What I'm hearing is that lots of water goes down the main downpipe, hits a flow restriction, then massively backs up. Like the rice in the funnel, or Wellington traffic. But you do have an backup outlet for the excess flow. I would be aiming for the main downpipe to only take as much water as it can naturally flow, and let the excess be managed by the backup. At least as a trial.

Eva888

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#3203437 5-Mar-2024 17:29

mdf:

neb: <snip> I really only need it on the main downpipe since the backup never gets that much flow.

This is probably counterintuitive, but have you tried restricting the flow on the main downpipe? What I'm hearing is that lots of water goes down the main downpipe, hits a flow restriction, then massively backs up. Like the rice in the funnel, or Wellington traffic. But you do have an backup outlet for the excess flow. I would be aiming for the main downpipe to only take as much water as it can naturally flow, and let the excess be managed by the backup. At least as a trial.

Don't know about anyone else but I just learnt what to do on a smart motorway. Double Duh, I thought the lower speed signs meant there are cars ahead slowing to 60 because of an accident so beware. No one ever told me about the jammed up rice theory.

tweake

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#3203441 5-Mar-2024 17:39

neb: When we did the Casa de Cowboy rebuild we replaced the Marley Typhoon guttering, which was totally incapable of handling the flow off the roof and would overflow, with commercial 100mm downpipes and guttering. Yeah, there's easily enough capacity. The second downpipe is 1-2m from the first one, it was put in as a backup in case one of the two gets blocked with debris or whatever.

this all sounds a bit suz. did someone actually do design work on this? or is this a case of just fit a bigger spouting to fix an issue?

what size roof aera, slope and length of guttering do you have? any pics of the 2nd downpipe setup.

i'm assuming it going to a tank, in which case i would not bother with any leaf catcher type system. simply have a tank vac overflow setup and it will suck all the leaves etc off the bottom of the tank and fire them out the overflow.

neb

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#3203443 5-Mar-2024 17:40

mdf:
This is probably counterintuitive, but have you tried restricting the flow on the main downpipe?

Yup, that was my original plan (see above), but I thought I'd get comments from people in case it was a crappy one, in particular the exact details of restricting the flow could produce a solution that's obvious (my 45x45 across the outlet idea) but wrong once it's subject to heavy rain. Certainly having another look at the Ultra-model leaf diverter is a good idea in case that solves it.

mattwnz

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#3203448 5-Mar-2024 18:02

tweake:

i'm assuming it going to a tank, in which case i would not bother with any leaf catcher type system. simply have a tank vac overflow setup and it will suck all the leaves etc off the bottom of the tank and fire them out the overflow.

How does that work? Is there a website or diagram showing this?

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mdf

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#3203454 5-Mar-2024 18:22

neb: Yup, that was my original plan (see above), but I thought I'd get comments from people in case it was a crappy one, in particular the exact details of restricting the flow could produce a solution that's obvious (my 45x45 across the outlet idea) but wrong once it's subject to heavy rain. Certainly having another look at the Ultra-model leaf diverter is a good idea in case that solves it.

Sorry, reading comprehension fail on my part. Missed that part of your original post.

tweake

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#3203462 5-Mar-2024 18:43

mattwnz:

tweake:

i'm assuming it going to a tank, in which case i would not bother with any leaf catcher type system. simply have a tank vac overflow setup and it will suck all the leaves etc off the bottom of the tank and fire them out the overflow.

How does that work? Is there a website or diagram showing this?

there is commercial products, Bunnings had a kit. there is the tank vac https://www.tankvac.co.nz/, there is a few variations on the theme.

basically all it is is extending the overflow down to the bottom of the tank. so when the tank overflows its pushing out water from the bottom of the tank. you just need a small hole to break the syphon effect so it doesn't empty the entire tank. that works reasonably well, but better ones have a fancy tube system so it collects all the crap a bit better. i did the simple version on parents house and it works ok. there is also the option of the tank vac device which creates a stronger overflow effect so even in low rain fall it will produces a strong overflow and clean it out better.

johno1234

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#3203467 5-Mar-2024 19:13

Damn that's clever.

mattwnz

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#3203475 5-Mar-2024 19:29

tweake:

there is commercial products, Bunnings had a kit. there is the tank vac https://www.tankvac.co.nz/, there is a few variations on the theme.

basically all it is is extending the overflow down to the bottom of the tank. so when the tank overflows its pushing out water from the bottom of the tank. you just need a small hole to break the syphon effect so it doesn't empty the entire tank. that works reasonably well, but better ones have a fancy tube system so it collects all the crap a bit better. i did the simple version on parents house and it works ok. there is also the option of the tank vac device which creates a stronger overflow effect so even in low rain fall it will produces a strong overflow and clean it out better.

Thanks that is an interesting system. Looks like the tank can't be an underground one as it looks like it needs gravity for the syphon effect which is a pity as mine is a concrete underground one.

neb

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#3203489 5-Mar-2024 20:04

mattwnz:
Thanks that is an interesting system. Looks like the tank can't be an underground one as it looks like it needs gravity for the syphon effect which is a pity as mine is a concrete underground one.

It's not a siphon, it's a simple overflow. In fact there's an air vent in the outlet to prevent it from turning into a siphon since you don't want it to suck the tank dry but merely spill excess water, so at most it's a siphon until there's a small amount of air space at the top again.

tweake

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#3203499 5-Mar-2024 20:22

mattwnz:

Thanks that is an interesting system. Looks like the tank can't be an underground one as it looks like it needs gravity for the syphon effect which is a pity as mine is a concrete underground one.

as neb mentions its overflow rather than syphon. however the tank vac system uses syphon effect. as long as a tank can overflow it will work. the hard part is getting access to the pipe work. i did it to my storm water dentition tank to help keep that clean but as its a tiny tank its all done through the hatch.

Bung

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#3203548 6-Mar-2024 06:35

neb: Yeah, there's easily enough capacity. The second downpipe is 1-2m from the first one, it was put in as a backup in case one of the two gets blocked with debris or whatever. When I checked when it was put in a year or two back you just couldn't get 100mm leaf catchers/diverters here, everything was 80mm or 65mm. .

Now that you mention it the 2nd railhead is just visible in the original photo. If that pipe isn't carrying much water your idea of limiting at the top of #1 is worth a try. I found one of my runs was limiting because the gutter wasn't fixed at far end and it had closed up in the railhead so there was just 2cm between gutter ends. Rather than odd bits of wood do you have any leftover bits of gutter?

neb

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#3203782 6-Mar-2024 14:05

Bung:
If that pipe isn't carrying much water your idea of limiting at the top of #1 is worth a try. I found one of my runs was limiting because the gutter wasn't fixed at far end and it had closed up in the railhead so there was just 2cm between gutter ends. Rather than odd bits of wood do you have any leftover bits of gutter?

Ah, that's a good idea, I might be able to butcher the 80mm-sized gutter or head to only allow 80mm-capacity flow through. My main concern is not having all the leaves build up there, but some slotted-in PVC will be a lot less of an obstacle than a piece of timber. Thanks, I'll have a look later and report back.

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