Ok, I know you haven't picked yet but can you narrow down your scupper choices to one or two types? It looks like most of the standard scuppers on there are 15-20GPM in flow rate and they have a 1-1/2" diameter attachment. You mentioned your PB/Plumber might use 2" PVC pipe, is that right? If so, they will have to neck down the piping at some point to connect the scupper.
So, if you have 3 scuppers, you're looking at a total flow rate of 60GPM max. Based on what I showed previously, even the smallest pool pump (1/2HP) would still have way too much pressure. You would definitely be better served by using a waterfall pump on the scuppers from an efficiency standpoint. At 60GPM total flow, even the smallest waterfall pump will provide more than enough head (~14ft TDH) to meet the need.
Here's what you need to do -
1. Discuss with your PB and plumber the reasons why they are choosing a pool pump to run the scuppers and not a waterfall pump. You can tell them you have a friend who's a propeller-head and has questioned the sanity of that approach by using.....shock
MATH ..... to determine that they are oversizing the pump relative to the need. Don't let them get away with saying, "
oh trust me, I build pools all the time and this is how we always do it!" or "
Internet advice?? You talk to people on the internet?? Tell me, do you get your medical advice from the internet?? Of course not!! Trust me Sweetie, I know what I'm doing because I'm a PRO-fessional, wink, wink..." If they truly think they know what they're talking about them ask them if they have any dynamic head calculations to backup their choice of pool pump and pipe sizing... (yeah, I can be a royal pain in the you-know-what sometimes...).
2. Find out how far down the wall the suction source will be for the scuppers and how far above the water surface the scuppers will be? I need total feet of vertical distance that you plan on raising the water.
3. Find out how far the pipe runs are from the pool to the pump and the pump to the scuppers and the diameter of all pipes being used. Also find out if there will be any 90-deg elbow unions used (that adds to the head loss).
By knowing all that information, one can easily calculate the TDH for the water feature (hint, hint, there's a website for that) and then, once you know the TDH, you can use those pool pump curves to figure out how much flow you'll have. Here's my bet - even after calculating all the TDH involved, I bet a mid-range waterfall pump will provide more then enough flow. In fact, I will go even further and say that you will still have to add shutoff valves to the scuppers to regulate the flow from one of those waterfall pumps because there will be too much flow.
At the end of the day, what all this means is that, if you go with a waterfall pump, you can probably save yourself a few hundred bucks (maybe) in pump costs and run a lower electricity cost pump. It will also operate more quietly than a pool pump but a 1HP pool pump is already fairly quiet. So you have to ask yourself if the costs savings is worth the hassle. Yeah, you'll probably tick off the PB a bit by "
gettin' all-up-in-his-business" but hey, you're the one laying out the money here so you deserve to get what you want.
Let me know what you decide to do.
Matt