Newbie to forum. Great place! Have enjoyed the reading and all of your expertise!
After reading the primers on this forum and at other sites, I find I am at a bit of a loss in determining the total head loss of my system and then determining the right size pump for my pool system.
I need to replace a 20+ year old 3/4 HP Hayward super-pump predecessor. Much of the pump is rotting out, and it cannot run long in hot weather without shutting down until it cools off.
While mathematically capable, I've seen many confusing sites and calculators. Considering my system components, I've gotten absurd numbers (of over 200 feet of head). So, clearly something in my understanding and the calculations is very, very wrong! Which is why I joined this forum seeking some answers.
Here is my system and a few questions at the end. Please ask any follow up questions! Thanks in advance!
Pool: 20' x 40' inground, vinyl liner, 8' max depth. Water volume approximately 29,000 gallons.
Pad location: the pad with pump, filter and heater is approximately 6 feet BELOW the pool deck. I'm guessing that the suction and return ports are about 3.5' above the pump, while the skimmer is more like 5'+ above the pump.
Lines: 1.5" black poly (with some damage that has been repaired with couplings). 2 suction (side wall in deep end and skimmer at mid point). 1 return (to eyeball in shallow end). No deep end center drain.
Pipe length: Deep end suction 65 ' to pump. Skimmer suction 50' to pump. Return line 35' from heater. Approximately 26' of piping at the pump/filter/heater pad and accounting for the vertical drop to the pad in all 3 lines. Total length of 1.5" pipe estimated at 176'.
Items impeding flow: seven 90deg elbows; one 45deg bend, one tee, at least seven couplings along the length of the 1.5" black poly. 2 two-way valves. 1 sand filter (Hayward 62 gpm rated) and multi-port valve. 1 heat pump. 1 skimmer. 1 return eyeball. All piping is 1.5" PVC or 1.5" black poly.
Current pump: 3/4 HP old Hayward (like the super-pump) with A.O. Smith motor.
I'd like to get a more energy efficient pump. A two-speed pump seems like the right choice, but the Hayward MaxFlo VS SP2302VSP seems like a heck of a lot better in total lifetime cost (even over just a few years). Based on pad wiring, I'd have to stick with 115V pumps, so that leaves out some reasonably priced models (Pentair 340042).
With the current old 3/4 HP pump, I get a decent flow around the pool and the skimmer works fairly well. (I worry about going to a very slow flow that the skimmer will no longer work.
- What is the head loss of this system (in several gpm flow rates)? How would I calcultate that?
- What size pump should I be looking for? 3/4 HP? 1 HP?
- At low flow rates, seems like my head loss (although I am calculating it wrong, I think) is way above any pump's curves - even at low gpm's. How can a VS pump handle my system? Or, what am I doing wrong to calculate total head loss?