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When I was trying to figure out TDH and flow rates for my pool, I thought I read that 2" pipe can only flow 72gpm. A friend of mine services a commercial pool that he says flows 100gpm through 2" pipe with a 3hp pump. Is there a true maximum 2" flow rate??
Hal
With a given pipe size you don't hit a brick wall at some flow rate. All it means is that to ram more water through a given pipe size you just need more pressure. Consider a fire hose nozzle where you want to throw a stream a great distance. More pressure. You don't want this in a pool circulation system. You want the lowest pressure and most flow therefore the largest pipe that is reasonable. Hope this clarifies things a little.
Al
Thanks, Al. All this concerns the church pool re-build. We have one main drain line (2") that's now teed to 2 drains 10' apart. This one line joins a wall drain (2") and goes to a 2hp pump and I was trying to guessimate the flow rate but will have to wait until the system's up and running and see what the flow meter shows.
Hal
What comes into play is that flow is a function of linear velocity in the pipe and for the purposes of noise and physical damage (at joints and bends) you don't want to exceed rated velocity in a piping system.
Check this post on the Hayward site. It deals with the hydraulics of sizing pipes, pumps and filters in a very easy-to-understand manner. You will see that the maximum standard flow rate for 2" PVC pipe is 105 GPM on the pressure side and 85 GPM on the suction side.
http://www.haywardnet.com/pdfs/Pump_filter_sizing.pdf
Depending on the total dynamic head and the pump curve of your 2 HP pump you could easily be exceeding the 85 GPM limit on the suction side. To be safe you could use 2.5" or better yet 3" PVC from the junction of your side and bottom drain lines to the pump. You should also look at your pressure side pipe sizing to be sure you are OK there as well. I would "guess" that you would need at least 2.5" PVC from the pump through the filter and out to any T's that split to your returns.