Is this flow calculation right?

[Mark917]

Posted this in another thread/location but it belongs here -

Need some math/pump assistance here. I currently run a Jebao DCP 18000 from my basement sump to a 40 Breeder in my kitchen. I am trying to back into what my actual flow rate is without a flow sensor or using a 5 gallon bucket and timing it.

- Pump Specs - Jebao DCP 18000, max flow is ~4700 GPH at 130 watts - 0 head loss.
- I am running it at level 57 and a 72 watt output.
- Overflow is Modular Marine bean animal setup with 1/2 inch drains. I am at full siphon on the Primary drain with minimal water through the Secondary drain.

See below for my calculations based on something I picked up on these boards around flow restriction through pipe. I'm assuming these flow restrictions were standard for any size pvc.

Current Output at 57% and 72 watts 2679 GPH

GPH loss calculated
Height (14ft vertical@75-125) GPH loss) 1750 GPH (used 125 GPH loss for calc)
Elbows (5 @ 50-75 GPH Loss) 375 GPH (used 75 GPH loss for calc)
Ball valves (2@30 GPH Loss) 60 GPH
Unions (2 @5 GPH Loss) 10 GPH
Total loss 2215 GPH

Total current flow based on above 464 GPH
Tank volume 40
Return turnover 22

Does my logic and all calculations make sense? So I'm running nearly 500 GPH through 1/2 inch full siphon?

 

[T-J]

EDIT: I entered my numbers wrong.

 

[theMeat]

Would guess around 400 without elbows and such is going down 1/2 full siphon.
Would also say most every pump manufacturer exaggerates gph, except maybe ehiem.
At 400 gallons that’s 10x display volume per hour. Personally would shoot for half that.
Ime any pump not rated for hi pressure will loose gph within a few months, a year tops, so keep an eye on flow over time.
Check out linky

How Much Water Can Flow Through A Pipe (GPM/GPH)?

Three tables to get a general understanding of water flow capacity through a pipe or roof drain. If you have questions, contact our roof Drain Wizard.

hy-techroofdrains.com

 

[Mark917]

Can that be right. Lets say there are 4 liters in every gallon (round numbers). Lets also assume that green line at 0 head is sitting at 15,500 liter/hour. That would be 3,875 gph at 0 head at 79 watts. Not great at math so did I miss something?

 

[Mark917]

Would guess around 400 without elbows and such is going down 1/2 full siphon.
Would also say most every pump manufacturer exaggerates gph, except maybe ehiem.
At 400 gallons that’s 10x display volume per hour. Personally would shoot for half that.
Ime any pump not rated for hi pressure will loose gph within a few months, a year tops, so keep an eye on flow over time.
Check out linky

How Much Water Can Flow Through A Pipe (GPM/GPH)?

Three tables to get a general understanding of water flow capacity through a pipe or roof drain. If you have questions, contact our roof Drain Wizard.

hy-techroofdrains.com

Agreed that's why i'd like to cut it way back here. Do the GPH restriction calcs look ok to you? If so I'll work from there and also take a conservative view of total GPH the pump can deliver which is a great point

 

[Mark917]

Agreed that's why i'd like to cut it way back here. Do the GPH restriction calcs look ok to you? If so I'll work from there and also take a conservative view of total GPH the pump can deliver which is a great point

BTW thank you for the chart. That is referred to here more than a few times and I have seen it but some folks argue that water falling more of a distance will add to that siphon/gravity force (velocity). This water is falling ~14 feet. That is way beyond my needs here and may not be material enough to impact this result.

 

[theMeat]

Agreed that's why i'd like to cut it way back here. Do the GPH restriction calcs look ok to you? If so I'll work from there and also take a conservative view of total GPH the pump can deliver which is a great point

Think instead of trying to figure how many gph your low pressure pump is giving at close to max head height, and whatever return plumbing restrictions you have...
Instead we know your drain is giving you 400 maybe a lil more, and a lil more yet with secondary drain. Which btw is pretty close to your calculations.
Imo more gph turnover through sump that what your skimmer can process is a waste, and let’s debris settle in fuge for consumption.

 

[theMeat]

BTW thank you for the chart. That is referred to here more than a few times and I have seen it but some folks argue that water falling more of a distance will add to that siphon/gravity force (velocity). This water is falling ~14 feet. That is way beyond my needs here and may not be material enough to impact this result.

Np yeah understanding the falling further has more weight pulling down. Chart shows 7 psi for its gravity calculation, would think that’s pretty close to what you have in 1/2 at 13 feet

 

[KrisReef]

Let me help.

 

[theMeat]

Let me help.

No joke.
Could time a 5 gallon bucket on drain and do the math

 

[Mark917]

No joke.
Could time a 5 gallon bucket on drain and do the math

I know that is probably the best way. Hand grenade close tho I think approximately 400 would be a good gauge. What it confirms is that I should slow it down (i.e. restrict the pump and the primary drain). Then I'll really screw up the calcs .

Thanks all!

 

[KrisReef]

assuming it is 400 gph,
5 /400 X 3600 the bucket should fill in 36 seconds.

This again is close to the charts.

 

[Mark917]

assuming it is 400 gph,
5 /400 X 3600 the bucket should fill in 36 seconds.

This again is close to the charts.

Now I'm just curious as hell how it comes out! Will put a line on the primary to see. I can just see myself already- iphone timer in one hand, hose in the other and not shutting it down in time . The things we spend our times doing in this hobby...we should all have honorary science/engineering degrees!

 

[Mark917]

I can actually conceive of it filling a gallon in 7.2 seconds (36/5). I think Ill try that one.

 

[KrisReef]

I've dropped my iphone in a tide pool and in my tank, both times for science. Godspeed!

Before you publish your results maybe we should add squares with times in them and let the community buy a square for a chance to win the pot?

 

[Mark917]

I've dropped my iphone in a tide pool and in my tank, both times for science. Godspeed!

Before you publish your results maybe we should add squares with times in them and let the community buy a square for a chance to win the pot?

Now that's an idea.