- May 3, 2007
- 17,002
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Given the number of times we have had to tell members that the 90s they are using are not sch40, it seems to be a fairly common mistake. Also, the sweep 90's you find in most home stores are not sch40.
Sweep 90's do reduce head loss and the more 90s you have in the plumbing, the more head loss is reduced. The gain is relative to the head loss in the 90s vs the head loss elsewhere. If you are getting a significant drop in filter pressure by switching to sweep 90s, that means you are using a lot of 90s in your plumbing designs. However, for a standard pool, with a typical layout, the impact of sweeps is significantly less. Given the difficulty and cost in building two identical pool plumbing systems with different types of 90s, the best way to compare the two designs is with a head loss model. Here is a an example that is similar to the OPs pool:
- 2x40' suction runs with equal flow (assumes elimination of the MD)
- 5x90 bends in each of the suction runs
- 5' pad pipe
- 5x90 bends on the pad
- 2.5 sq-ft filter with 2" Multi-port
- 1x40' return run
- 5x90 bends in return run
- 5 return ports split at the pool
Given that the filter is only 2.5 sq-ft, the flow rate should not exceed 50 GPM so for the head loss model, I used 1500 RPM for the Ecostar pump. Here are the operating points for a standard 90s vs sweep 90s for ALL the 90s in the plumbing.
Standard 90s: 46.81 GPM @ 14.16' of head & 220 watts - Filter Pressure: 3.42 PSI
Sweep 90s: 48.34 GPM @ 14.01' of head & 224 watts - Filter Pressure: 3.41 PSI
So you can see there is very little difference between the two scenarios. Sweeps have about 1/2 the head loss of standard 90s but because other pieces of equipment have far more head loss, especially a 2.5 sqft sand filter, it doesn't add up to a big change overall. But again, if your pools have 10x the number 90s, then obviously you would see a larger difference. But then I would have ask why you are using so many 90s in your design.
Actually, there is not much of the gain that is lost with bushings. At 50 GPM, a 2" to 2.5" bushing has only about 0.05' of head loss. Insignificant even when accounting for four of them.
Note: The head loss model I am using has been validate with close to dozens pools over the last 12 years. So I am very confident in it's accuracy. It primarily uses the fitting minor losses from the Crane TP-410 "Flow of Fluids Through Valves, Fittings, and Pipe" handbook.
@orangepower10, One of the issues that you will run into is that the flow rate for the waterfall will exceed that of the recommended flow rate of the filter. So either you are going to have to up size the filter or you will need to plumb a bypass to prevent over driving the filter when in waterfall mode.
