Hi,
wasn't sure whether to bump this old thread or start a new one.
I am looking to have pump-free ponds with the new ones now under way (after what seems an age, digging started last week).
Having read everything I can find I am still unsure what size lifts to have and whether before or after the filter.
I found an Excel spreadsheet on a US site giving the amount of air required to move a given volume of water up a given size pipe.
I have added a more friendly front end on it.
It seems to contradict some of what I have read here.
Unfortunately I can't upload spreadsheets here to let you see - anyone know how to allow this?
My big dilemma is whether to put the lift on the riser from my bottom drain, or on the return to the pond.
The riser from the bottom drain has advantages in that it is deeper, so I can get the air further below the water surface, so can lift more water for the same amount of air.
Ideally I would use the whole 110mm pipe as the lift, but the spreadsheet says I will need over 3 times more air to lift the same amount of water than if I use a smaller pipes.
The sweet spot seems to be 32-50mm diameter lifts.
According to the spreadsheet, to move 5000 lph where the air is injected 1m down and the required lift is 100mm.
32mm pipe requires 35 lpm
40mm pipe requires 34 lpm
50mm pipe requires 38 lpm
75mm pipe requires 63 lpm
110mm pipe requires 122 lpm
Now ideally I want to move twice this as the pond will be about 14000l.
I could get 3 x 40mm pipes down the centre of the 110mm pipe, or as many as 7 x 32mm, so in theory could move all that I need to.
Can anyone see any disadvantage in having smaller diameter pipes in the feed to the filter?
I can only think of blanket weed (which I hope to avoid).
As has been mentioned several times, the amount of lift required makes a HUGE difference.
Theoretically you can lift up to 50% of the distance the air injection is below the water surface.
So you could lift 500mm with a 1m injection - flow would be very low though. A bit like the max head figure for a pump.
Reducing the lift in my example to 50mm, but keeping the 1m submergance, more than doubles the flow.
So, according to the spreadsheet I can get 10000 lph through a 40mm pipe with 33 lpm of air - this I do find hard to believe!
Or, 5000 lph with only 18 lpm of air
If I go for the lift on the return, I can only get about 750mm submergance.
In my first example with 5000 lph and 100mm lift this increase the air required from 34 to 43 lpm
And in the last with 50mm of lift it increase from 18 to 22 lpm.
I hope this adds to the information pool, rather than just be my ramblings
Has anyone else's experience moved things on and does anyone have any ideas as to my before or after the filter quandary?
Thanks
G