How much height do you need for gravity return to a pond?

[Mmathis]

I think I’m trying to figure out slope, maybe, but my math skills are…..well, I don’t have math skills.

 

[TheFishGuy]

for a stream it is a minimum of 1-2" of elevation change per 10ft. Not a ton at all.

 

[combatwombat]

Are we talking via pipe? Or an open stream flow like @TheFishGuy mentioned?

 

[Mmathis]

Are we talking via pipe? Or an open stream flow like @TheFishGuy mentioned?

More than likely, PVC.

 

[clark kent]

Your basic plumber's rules of thumb would apply, wouldn't it. Under 2 1/2 inches in diameter - 1/4 inch per foot. 3 to 6 inches in diameter - 1/8 inch per foot.

 

[Lisak1]

Well, in my mind if you have a pump on one end... oh wait. You said "gravity". Not only are my math skills bad, my reading skills need work, too!

 

[Mmathis]

@Lisak1 YOU JUST MADE MY DAY!

 

[GBBUDD]

1/8 inch per foot is the basic pitch for drain lines that way the water doesn't run out of the pipe leaving any solids behind but I believe you'll have a constant flow of water so there realy isn't a degree of pitch.

 

[Mmathis]

1/8 inch per foot is the basic pitch for drain lines that way the water doesn't run out of the pipe leaving any solids behind but I believe you'll have a constant flow of water so there realy isn't a degree of pitch.

Good to know! One option I have considered is to use large Rubbermaid stock tanks for the bog(s) as opposed to excavating and using a liner. I am still using my original Skippy (no judgement, it works for me has been going strong for 10 years — OMG, has it been that long?) to filter the goldfish pond/pool, and I am very accustomed to the way it’s plumbed as well as its idiosyncrasies. I have a 300 gal tank that used to be for QT back at the old place, and I think it might work as a turtle-bog. Whenever completed, the edge of the Pond and water level will be slightly above ground level (high water table), so need to be sure I can account for a good gravity return.

 

[combatwombat]

Just about any pitch will work. With gravity flow returns, the real thing to look for is flow rate. Need to know what you need to flow and then choose pipe size appropriately. Need bigger pipes for gravity than for pump.

 

[ingypingy]

Just about any pitch will work. With gravity flow returns, the real thing to look for is flow rate. Need to know what you need to flow and then choose pipe size appropriately. Need bigger pipes for gravity than for pump.

Reviving this one, as it's halfway to answering a question that's been bugging me... Do you know how to size the pipe to gravity feed back from a raised external bog filter to the pool? I'm sure there must be a formula or a table or such, but my search terms for Google must be missing the mark... Very grateful for any ideas (I'm expecting about 8000 litres/hour from the pump, and it's about 60 cm back down the to pool a few metres away...)

 

[JRS]

Perhaps this might help https://www.calctool.org/fluid-mechanics/pipe-flow#gravity-flow
From this thread: https://www.koiphen.com/forums/show...GPH-for-2-quot-pipe-gravity-flow-30-feet-away

I came up with 1.5 inch pipe minimum if I converted everything correctly

 

[GBBUDD]

Gravity out feeds are nothing but potential problems imo in a bog scenario. Plants can grow and die so fast they can block a pipe or three in one action like falling over and a few leaves blocking the pipe. I HAVE HAD THIS HAPPEN IN THE BOG WITH A WEIR output and had it almost cause a problem and my weir is 24" wide at the water level and 5 feet above that, yet the water level rose.