What pump should be used for a 5000 gallon aquaponics system?

Question

I am installing a new aquaponics system. It will have 2 650 gallon fish tanks, 1 1500 gallon sump, 1500 gallons of flood and drain grow beds, and 3000 gallons of DWC beds. The fish tank and sump tank will be buried in the ground with their tops flush. The fish tank is 2' tall. The sump is 6' tall. From the ground up to the top of the grow beds is 2'. The DWC top is 12" off the ground. I am planning on using gravity as much as possible. The system will consist of 4 rows of beds. The fish tanks are on one end and the sump on the other end. The fish tanks will protrude from the ground about 12". The sump will be buried flush.

The idea being that I will pump out of the sump up to the flood/drain grow beds. This will do a normal auto-siphon out which will gravity feed into the DWC beds. This will flow from one end of the bed to the other and gravity feed into the fish tank. The overflow from the fish tank will gravity feed over to the sump.

Let me know if this is enough information to point me in the right direction for the appropriate pump. I can provide more details as needed.

EDIT What pump brand / model would be suggested for a continuous running system to circulate the water at least once per day or not more often. Has anyone tried a pool style pump?

Answer 1

Added at top May 2016:

@Johann commented on May 20th :

Please note that the Question is talking about an Aquaponics system, not Hydroponics. The entire water system needs to completely recirculate at least once an hour due to fish/oxygen needs. Your pump will be a very large one or a multi staged set up.

This suggests that while my advice may be correct for a given flow rate, the desired flow rate is much higher than I assumed. The actualtime to circulate all fluid is an importnt parameter nd must be specified by the 'client'.

A quick update based on that, is that my power required formula still holds as an approximation. ie

• You will get about 66 litres per hour per Watt in your system.

• Divide litres by ~~= 4 to get US gallons.

So, if 1 hour circulation time is required.

Power = Gallons_per_hour / 16.5 Watts

For a 5000 gallon system = 5000 /16.5 = 300 Watts or about 1/2 HP.
As the volume involved appears to be more than 5000 gallons (adding up the various tanks & beds) then perhaps a 750 Watt / 1 HP pump may be needed for once per hour circulation.

---

Engineers view :-).
Replace with answer by somebody with practical hydroponics experience when available.

You can determine desired flow rate needed from hydroponics lore.
Let's say the system = 5000 gallons or 20,000 litres (4:1 is close enough for this purpose). To recirculate the total fluid in 1 week = 168 hours requires 5000/168 = 30 gallons per hour or about 120 litres per hour
(= 2 litres/minute or 33 cc/second - about 1/3 of a 100cc medicine measure per second.
Not very fast.)
According to the formula in part (2) below that would requires about 120/66 or about a 2 Watt pump.
That's very small.

Taking the other approach - a 50 Watt pump will supply about 50 x 66 = 3300 litres per hour. Total system fluid will recirculate in about 20,000l/3300 = 6 hours.
If 6 hours is acceptable then a 50 Watt pump will be adequate. That sizing was probably conservative so I'dd expect you'd actually get substantially more flow and quicker turnover than that if required.

Say flow wanted = L litres/hour. Lift from top of sump if full to grow bed = 2 feet.
If you want to be able to pump with simp only half full = 3 feet from top, required lift = 5 feet. Say 1.5 metres. If you want to be able to pump sump from very bottom you need more power or be willing to accept a lower flow rate (probably acceptable).

So say Lift at full flow = 1.5 metres = height = head = h

(1) The easy way.

Pump manufacturers provide lift x volume charts and these can be used to select required power.

(2) The slightly harder way. In your case -

• Power ~~ = (litres per hour) / 66 Watts

• You will get about 66 litres per hour per Watt in your system.
  Divide litres by ~~= 4 to get US gallons.

Why ?
Read on ...

Pump power at 100% efficiency ~= head x litres/second x 10 Watts
litres/second = litres/hour/3600. For system with less than 100% efficiency multiply power needed by K. K = 100/efficiency %.
eg 50% efficiency -> k= 2.
25% efficiency K = 100/25 = 4 etc.

So Power = metres lift x litres / hour * 10/3600 * k

Assume k-5 for now = 20% efficient = easily achieved.
This includes pipeline head or pressure losses at typical flow rates.

Power = lift x litres /h x 50/3600 = h x l x 0.0139
Close enough to start:

• Power = lift x litres per hour / 100

• For 1.5m lift Power = litres per hour / 66

• or litres per hour = 66 x Watts.