Sizing the outflow pipe from a raised bog filter

[ingypingy]

Hi folks! I am in the early stages of converting an old in-ground swimming pool into a natural pond, using a couple of above-ground bog filters. The crux of my question is how to size the outflow pipe from the big back to the pool.

For each bog, I'm using a 10,000 litre/hour rated pump (maybe 8000 l/h with head and losses accounted for). The water will flow through 3x half IBCs and then back into the pool.

I'm sure there must be an equation (or general wisdom) to determine the size of the return pipe to simply gravity feed back to the pool (approx 0.7 meter drop)... Most of what I can find requires pressure as part of the formula. I did find this Hazan-Williams calculator, but there is a note that it's not accurate for pipes below 50 mm, and I have a hunch that's around the margin of what I'll need...? Grateful for any tips!

 

[j.w]

@ingypingy

 

[Laaf]

A pipe will be at risk of clogging.

A waterfall weir, or a larger wall that is lower than the bog water level and waterfalls back into your pond are less likely to clog.

I started with pipes, but they kept clogging leading to overflow on the sides and back of my bog.

Make more opening than you think you need. And make the other walls higher than you think.

I swear water defies gravity at times in my bog and flows up and over even though the usual exit path seems lower than where it is overflowing. Plants can create dams and if it happens overnight your water can flow out of your system.

 

[netvine]

so each ibc half will be a bog, 8000l/h at the input? what size pipe is input?

#1 FlexPVC®.com Water Flow Charts Based on Pipe Size (GPM/GPH) ie, How much water can flow through Sch 40 Pvc Pipe Size 1/2" 3/4" 1" 1.5" 2" 2.5" 3" 4" 6"

Water Flow Volume for a given pipe size based on charts, tables, formula, nomograph, & experience.

flexpvc.com

this might help.

 

[ingypingy]

A pipe will be at risk of clogging.

A waterfall weir, or a larger wall that is lower than the bog water level and waterfalls back into your pond are less likely to clog.

I started with pipes, but they kept clogging leading to overflow on the sides and back of my bog.

Make more opening than you think you need. And make the other walls higher than you think.

I swear water defies gravity at times in my bog and flows up and over even though the usual exit path seems lower than where it is overflowing. Plants can create dams and if it happens overnight your water can flow out of your system.

Interesting! What does the pipe get clogged with? Just plant roots?

 

[ingypingy]

so each ibc half will be a bog, 8000l/h at the input? what size pipe is input?

#1 FlexPVC®.com Water Flow Charts Based on Pipe Size (GPM/GPH) ie, How much water can flow through Sch 40 Pvc Pipe Size 1/2" 3/4" 1" 1.5" 2" 2.5" 3" 4" 6"

Water Flow Volume for a given pipe size based on charts, tables, formula, nomograph, & experience.

flexpvc.com

this might help.

Oooh! Champion! I think the first table is the answer... Thank you!

(To clarify, there will be three half IBCs per bog "unit"... The water pumps into the first, cascades into the second, cascades into the third, and then somehow (tbc, ha ha) returns to the pool)

 

[GBBUDD]

A pipe will be at risk of clogging.

A waterfall weir, or a larger wall that is lower than the bog water level and waterfalls back into your pond are less likely to clog.

and hands down far more rewarding it gives more sound , more action, mesmerizes the viewer.

I started with pipes, but they kept clogging leading to overflow on the sides and back of my bog.

Make more opening than you think you need. And make the other walls higher than you think.

I swear water defies gravity at times in my bog and flows up and over even though the usual exit path seems lower than where it is overflowing. Plants can create dams and if it happens overnight your water can flow out of your system.

i have seen too many systems with a pipe sticking out of a bog or shower or even three pipes ! why? when you can make a sheet flow or bouncing waterfall

 

[ingypingy]

Thanks GBBUDD - food for thought... I think I have some structural issues that will restrict the possibility of a waterfall... But I'll give it some further thought...

 

[Laaf]

My pipes got clogged with a combo of roots, leaves, plant stems, and pea gravel mixed in with all of it. Oh, plus some ice in winter.

It took much less debris than I expected to partially obstruct the pipe and make the water level in the bog rise.

Pipes flowed easily at first. But once it was an issue......it was unpredictable and sometimes clogged over night.

 

[ingypingy]

My pipes got clogged with a combo of roots, leaves, plant stems, and pea gravel mixed in with all of it. Oh, plus some ice in winter.

It took much less debris than I expected to partially obstruct the pipe and make the water level in the bog rise.

Pipes flowed easily at first. But once it was an issue......it was unpredictable and sometimes clogged over night.

Thanks! That's really useful info... I don't think I'll be able to avoid using a pipe, but I'll definitely try to incorporate some stuff in the design to prevent blockages! And make it easy to dismantle/clean the pipe...

 

[Laaf]

Redundancy such as multiple pipes could help. So if one clogs, there are other outflows.

When I said water defies gravity, it is because there is an opening lower than the level the water rises to. Due to the gravel, debris and friction, the water in my bog is higher than at the opening I made for outflow.

Blockage and friction raise the water level much higher than I expected. I thought water would always flow to the lowest spot. Sure, it flows to the lowest spots. But add plants etc and.........water level is higher at the back end of my bog than at the front, even with an exit path for the water to take.

If that makes any sense................

I told my husband it doesn't make sense to me since water should be level to gravity. And he said I forgot to take the resistance and friction into consideration.

Most of us do not use equations here, just trial and error and advice from others.

 

[Lisak1]

Most of us do not use equations here, just trial and error and advice from others.

And in my case - a whole lotta luck!

 

[GBBUDD]

Me just stubborn as all hell and work through it