Question about water pump and head

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T

toffee

Candiru
MFK Member
Aug 21, 2006
159
8
48
Texas
I am converting an inground concrete spa to a pond.

1. The spa is about 5 ft deep,
2. about 10 ft away from the spa is a separate inground mechanical area about 6'x6' and about 7' deep.
3. pump is placed in the mechanical area, 3ft above from the floor or 4ft below spa's water level.
4. I want the water to pump to some kind of waterfall structure that is 4ft above spa's water level.

So, is the head 4ft + 4ft = 8 ft? or 4ft

Thanks for helping.
 
Discharge head is 8'. Total head is 4'. You discount the contributed energy from the suction because you only want to consider energy from the pump only. If you are not getting flow it is more likely your pipe size or restriction on the suction side. Being ten feet away also plays a part.
 
toffee said:
what's the difference between discharge vs total head?
Click to expand...

Total pressure is the difference in suction head and discharge head. Discharge pressure is dependent on pressure available on the suction side.

Pump performance is influenced by both the suction and discharge as you have seen. Pump install above the pool or below makes a difference on the output and pumping it above the pool (waterfall) reduces flow.

Consider tanks with sumps:
Suction head pressure is almost zero because there is not great volumes of water in the sump and being next to or in the sump, restriction is near zero. However, on the pump output side most people pump the water to the top of the tank so discharge head pressure would be the height from the pump to the top of the tank.

Consider closed loop filters (canisters):
For discussion eliminate fiction loss.
Tank water is pushed into the pump (free energy) on the suction side. Pump pumps the water back to the top of the tank. Total head pressure is less than the sump system because you minus the free energy on the suction side.

In you case, the pump being below the pool helps your total head pressure.
 
kendragon said:
Discharge head is 8'. Total head is 4'. You discount the contributed energy from the suction because you only want to consider energy from the pump only. If you are not getting flow it is more likely your pipe size or restriction on the suction side. Being ten feet away also plays a part.
Click to expand...
I don't quite understand this. Even though the water may be siphoning in from the higher spa, the pump still has to lift the water 8 feet to the top of the waterfall. Add in friction loss and any elbows or plumbing restrictions and the total head has to be more that 4 feet.
 
joe jaskot said:
I don't quite understand this. Even though the water may be siphoning in from the higher spa, the pump still has to lift the water 8 feet to the top of the waterfall. Add in friction loss and any elbows or plumbing restrictions and the total head has to be more that 4 feet.
Click to expand...

Read my other post. For discussion I didn't consider the friction losses. Yes, you are correct about the plumbing adding to the total head.
 
SpaPond.gif

OK, this is roughly how the Spa2Pond is laid out. The bottom drain is connection to the same collecting area with the skimmer. I notice most water was drawn from the bottom drain with minimum from the skimmer (90/10?), and it is about 15-18 ft from the pump. Pine size is 1.5", except the pump is 1.25".

I am using a little giant Flex Pumps FP1, 1920g max. 5ft at 1000g and 10ft at 390g. The spa is about 500g.

Not sure why the water is somehow slower than expected.

SpaPond.gif
 
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