Need help critiquing poor plumbing to PB

[Ironic]

It is fine to use equivalent length of pipe when estimating head loss in the pipe and fittings but this is NOT the same as head loss. It just gets you one step closer. You then need to calculate the head loss at a specific flow rate BUT that too is not really correct because you need to find the crossover between the pump's head curve and the plumbing head curve. My first estimate for your plumbing head curve is:

Head (ft) = 0.004 * GPM^2

Note that this has a head loss of 40' at 100 GPM but if you use your 150 GPM goal, the head loss becomes 90' of head. Double what you calculated. This of course is not on the Intelliflo's head curve as I showed above. This is why you must use a plumbing curve to determine the actual operating point.

If you plot the plumbing curve over the pump's head curve, where they cross is the operation point which I showed in my previous post. But I did not have your fitting count so it may be slightly off.

I am having a hard time figuring out what you exactly what you did to see where you went wrong. What was your total equivalent length of pipe and what was the GPM that used to determine head loss?

How did you treat the parallel pipe vs the series pipe? Head loss adds with pipe in series. However, when pipe is in parallel, it is much more complicated. The head loss in each pipe must be the same because they share the same input and the same output node. Also, the total flow rate splits into the separate pipes so the resulting head loss is less than if a single pipe carries all of the flow.

Also, a swimming pool "rise" only occurs for water falls and slides. The rest of the plumbing has no rise as it is canceled out by an equal fall.

Also, everything that touches the water adds head loss so skimmers, MDs, eyeballs, exit pipe etc. I don't see these in your calculations.

As I said before, this is not a trivial calculation.

If I get some time, I will update my calculation with your fitting counts.

Whoa! Ok. I understand the graph you made much better now.

I used 70 GPMs in calculations (as the blog gave predetermined equivalent feet for that flow), and I didn’t account for series or parallel. 2 returns are in series on the left and 2 on the right. 1.5” all the way. Everything else unaccounted for was because I didn’t have that data or know the equations to determine.

I just realized that I only estimated feet of head for the suction side!

 

[mas985]

A couple of follow up questions:

You have what looks like 3 return lines. How many eyeballs on each return line?

The two return lines that you show together (2x), are they actually separate runs pool to pump or are they split at the pool?

In reality it isn't going to matter much. If all the return lines are open, the head loss in those sections are insignificant. Same for the suction lines. Most of the head loss is in the pad equipment. At best, the plumbing curve will be closer to:

Head (ft) = 0.0035 * GPM^2

Or slightly better than my original estimate. But as you adjust the valves for each of the water features, the plumbing curve will increase so it may not be far off from my first estimate.

 

[Ironic]

A couple of follow up questions:

You have what looks like 3 return lines. How many eyeballs on each return line?

The two return lines that you show together (2x), are they actually separate runs pool to pump or are they split at the pool?

In reality it isn't going to matter much. If all the return lines are open, the head loss in those sections are insignificant. Same for the suction lines. Most of the head loss is in the pad equipment. At best, the plumbing curve will be closer to:

Head (ft) = 0.0035 * GPM^2

Or slightly better than my original estimate. But as you adjust the valves for each of the water features, the plumbing curve will increase so it may not be far off from my first estimate.

One of those three 1.5” returns is for only the bubblers.
Two 1.5” returns from pump to pool with x2 eyeballs on each (4 total). First eyeball on each line splits off of a tee.

Based on that plumbing curve then, there is no pump that can handle our setup (returns + water features running simultaneously)?

 

[mas985]

The Intelliflo3 could produce 130 GPM on that plumbing which is less than what everything needs at the maximum rate. However, you don't really need to run everything at the maximum rate either. You could sacrifice some of the flow on some of the features when running everything at once. It is just a 15% decrease. with your current pump, you need reduce by more.

However, if you go with the intelliflo, it would be prudent to upsize the pad plumbing to at least 2.5" to reduce the water velocity some.

 

[Ironic]

@mas985 I just wanted to update and thank you endlessly for your time and expertise!

We bought the Intelliflo3 and upsized the pad plumbing to 2.5”, per your recommendation. My husband replumbed the entire pool himself, where he could the best way he could. He has some spots where he has regrets lol, but it made both of us feel so much better about pouring 1,500 sq ft of concrete over all of it! Now watch one of the lights spring a leak! Ha!


The electrician did some questionable things, but that’s a story for another thread I suppose lol


Thanks again! You’re the best!