Need help selecting the right gph pump for my system

[samtheman]

I am using a Mag drive MD7 on my system, I am not sure if I calculated it properly for my system, I have a 100 gallon sump, three 100 gallon growbeds, and 360 gallon fish tank. the height of my fish tank is 40". The flow to the growbeds are good, but the flow of water going back to my fish tank is very little. My setup is based on a CHOP2 system. Water from my fish tank returns to the sump by gravity. The pump at the sump feeds the growbeds and the leftover goes back to the fish tank. I am not sure if I should buy a bigger gph pump or adding another pump that can pump the water from the sump to my fish tank to increase the flow of water coming out by gravity :?

[davidstcldfl]

Hi Sam, lots of variables ....1st, we need to look at the performance chart for your pump...
http://www.aquaticeco.com/images/static ... es/MD2.gif (http://www.aquaticeco.com/images/static/pump-curves/MD2.gif)
You said your tank is 40 inches tall, lets add a little height for resistance of water going through your pipes. Say 5 ft...according to the chart, you are getting just under 500 gallons an hour. That should be [i] a good starting point. ( in theory...you could be getting 125 gph in each GB, plus the FT)

Just so we are all on the same page, here is a drawing of a chop 2 system...
http://www.ecofilms.com.au/2010/10/28/a ... -revealed/ (http://www.ecofilms.com.au/2010/10/28/aquaponics-chop2-revealed/)

Sam, whatever flow of water is 'going into' the fish tank, has to be coming out. If you have a ball valve at the fish tank and at the grow bed(s), [i]you could cut back on the flow to the bed(s) and increase the flow to the fish tank.
However....This will slow down the 'fill time' for the GB's...your bell siphons may not kick in, due to lack of incomming flow (?)



Is there a problem with the fish and/or system ? or your just concerned because it doesn't look like much flow into the FT ?
Are you concerned with the DO ? Do you have a spray bar on the water going to the FT ?
You might consider a small air pump in the FT. If you get one with a built in battery backup, that will be an added safety measure.

Of course, you already ran your pipes...I try to go one size bigger on the supply line, from the pump. This gives 'less pressure/resistance' and a little more flow.
Also, keeping the amount of 90's to a minimum helps. I use 2- 45 degree fittings together, instead of one 90 degree. Yes, it's kind of overkill...but it is less resistance.

Lots to consider...

[kneedeepinwater]

From my experience when it comes to pumps the gph and flow you are looking for I have always learned to go bigger. If I calulate I need 2000gph turnover, I'm probably going to look for a pump close to 4000gph as possible. You lose flow from all types of things even 90's like David said. I practice the same thing he does and use 2 45s where ever a 90 would be going.

Not trying to get off topic, but after reading some peoples comments about Chop2 I was wondering if some things could be done different. For instance the overflow that is drained back to the sump could you not have it drain back into the growbeds?

If you are going to have it drain back in the sump how about put baffles in your sump like saltwater tank sumps have. Have the water drain at the far end of the sump and your pump at the other far end to pump back to the grow bed and fish tank. The baffles might help trap some of the solids (just like detritus is trapped in saltwater sumps, does require some cleaning out here and there though) and you could also put some type of media between the baffles to help with further filtration. Just an idea.

[cedarswamp]

Hydraulically speaking the friction loss difference between 1-90 or 2-45 is non-existant.

[samtheman]

Is there a problem with the fish and/or system ? or your just concerned because it doesn't look like much flow into the FT ?
Are you concerned with the DO ? Do you have a spray bar on the water going to the FT ?

Lots to consider...

David, thanks for your quick response. I am running an air pump for my fish tank. I am not sure if I can call it a problem, is more like a concern, but it could be later on: two out of the three growbeds are filling up and draining within 16 minutes which I understand is good I think. My third growbed is filling up and draining in 35 minutes, and I did that in purpose in order to get water back to the fish tank, if I adjust my third growbed to fill and drain within 16 minutes then I get no water going back to the fish tank at all. My question is : is it good or bad to fill my third growbed in 35 minutes or is that harmful in some way?

[davidstcldfl]

Hydraulically speaking the friction loss difference between 1-90 or 2-45 is non-existant.
Hi Cedarswamp, there are sevearl charts online showing pressure loss in pipes and fittings. Here is a link to one of them.....
http://www.engineeringtoolbox.com/pvc-p ... d_801.html (http://www.engineeringtoolbox.com/pvc-pipes-equivalent-length-fittings-d_801.html)

[davidstcldfl]

if I adjust my third growbed to fill and drain within 16 minutes then I get no water going back to the fish tank at all. My question is : is it good or bad to fill my third growbed in 35 minutes or is that harmful in some way?

No set answer for that Sam....'generally', I would think once a plant is established, 35 mins wouldn't be that big of a deal. You'll have to keep an eye on the plants.
Maybe you could slow the flow into the 2, that are filling quicker ...sending more to the 3rd and to the FT (?)

Your 100 gal GB's 'should be' holding aprox 40 gallons of water each, due to the displacement of your media.
If my math is correct... :? ...you would need 160 gph going into each bed, to fill in 15 mins. This would leave no flow for the fish tank....considering, your pump's performance chart was showing 480 gph at 5 feet of head.

Sorry Sam.....if playing with the flow to the grow beds doesnt work, you may need a second (smaller) pump to send water just to the FT. If you get a 2nd pump, consider adding a spray bar to it.

[samtheman]

Thanks David,

I am going to play with the flow on the 2 growbeds and slow them a little bid and see what happens.
Men!!!, It's tornado weather right now in Orlando. I am going to try it tomorrow morning.
thanks again! :)

[cedarswamp]

Hydraulically speaking the friction loss difference between 1-90 or 2-45 is non-existant.
Hi Cedarswamp, there are sevearl charts online showing pressure loss in pipes and fittings. Here is a link to one of them.....
http://www.engineeringtoolbox.com/pvc-p ... d_801.html (http://www.engineeringtoolbox.com/pvc-pipes-equivalent-length-fittings-d_801.html)


Sorry I was speaking in terms of practical backyard application. The added turbulance created by the extra joints will negate any savings you realize from using the 45's. I do hydraulic calculations for my job.

[keith_r]

Hydraulically speaking the friction loss difference between 1-90 or 2-45 is non-existant.
Hi Cedarswamp, there are sevearl charts online showing pressure loss in pipes and fittings. Here is a link to one of them.....
http://www.engineeringtoolbox.com/pvc-p ... d_801.html (http://www.engineeringtoolbox.com/pvc-pipes-equivalent-length-fittings-d_801.html)


Sorry I was speaking in terms of practical backyard application. The added turbulance created by the extra joints will negate any savings you realize from using the 45's. I do hydraulic calculations for my job.

what kind of hydraulic calc's? just curious,, i spent some time designing fire protection systems..

[cedarswamp]

I'm certified in water based fire protection system layout, also in inspection and testing of water based systems.





Hydraulically speaking the friction loss difference between 1-90 or 2-45 is non-existant.
Hi Cedarswamp, there are sevearl charts online showing pressure loss in pipes and fittings. Here is a link to one of them.....
http://www.engineeringtoolbox.com/pvc-p ... d_801.html (http://www.engineeringtoolbox.com/pvc-pipes-equivalent-length-fittings-d_801.html)


Sorry I was speaking in terms of practical backyard application. The added turbulance created by the extra joints will negate any savings you realize from using the 45's. I do hydraulic calculations for my job.

what kind of hydraulic calc's? just curious,, i spent some time designing fire protection systems..

[davidstcldfl]

I'm certified in water based fire protection system layout, also in inspection and testing of water based systems.
Wow,that's a cool job :D I went through schooling in the union to become a pipefitter, then spent a few more years in school, cross-training into hvac.
In hvac, it's very critical concerning flow, so I guess I'm over focused on it :lol:

Your right, in backyard systems, it's not that critical. Just going up 1 size in pipe would be more then enough, to help to keep the flow rate up.

You wrote...The added turbulence created by the extra joints will negate any savings you realize from using the 45's.
I'm not saying your wrong..I very well could be wrong, I 'm trying to learn. I look at the flow chart, which shows flow restriction (turbulence)... and see 2 - 45's normally have 'less then' 1/2 of what a hard/pressure 90 does. Perhaps being 'near' each other 'creates more' (an exponential curve) flow restriction/ turbulence...then they would 'separate', elsewhere in the same given system ?

Your study of flow is more in depth, then mine....Do you have any info/links that you could please send to me, in regards to this ?
Thanks Cedarswamp.

Sam, I'm so sorry for going off on a rabbit trail with your posting... :oops: .

[samtheman]

Didn't have too much luck adjusting the flow of the growbeds, have you guys had any luck with the intex pumps and what model?
I was looking at the intex 637r (1000gph) for $40.00 online but not sure how efficient it can work on a aquaponics setup.