Your customers all tell you how much their electric bills are? Wow!

All of my piping is either 1 1/4" or 1 1/2". I hate it! If I had the cash to do so, I'd tear all of it out and replace with new 2" pipe.

It is meaningless to look at a pipe size in isolation. I would choose multiple and individually adjustable 1.5" runs over a single 2 " run any day.

Please explain your rationale

I think he means that you can individually turn on/off the pipes separately. That makes sense for something like skimmers and floor drains where you might want to separately turn one off. The two 1.5" lines are equivalent to a single 2".

Of course, if I had my choice, I'd have two 2" lines in that case. When my solar system is on and I'm running at 48 GPM, my Intelliflo VF is at 3000 RPM and consuming 1500 Watts. I have long 2" pipes going to/from the solar system and wish I had 2.5" or even 3" instead. Similarly to/from the pool, I have 1.5" separate lines to skimmer and floor drains and a 2" from the pump that splits near the pool into three 1.5" for the returns. I really wish the PB had used larger pipe throughout, especially for the longest runs. Though I've cut my electricity costs in half when I got the variable speed/flow pump, I could be saving so much more using larger pipe, at least when the solar is running (when I'm at 26 GPM with no solar, I'm at 275 Watts). With marginal electricity rates from PG&E in California now hitting 42 cents per kilowatt-hour, getting the same flow at lower head and therefore far lower cost is a big deal.

Pipe diameter is only one aspect that determines head loss although it is quite significant (~5th power of diameter). But if you split the flow rate through multiple pipes, the head loss can actully be less than a single larger pipe. Here is a chart which shows the equivalent pipe diameter for multiple pipes (uses Hazen-Williams formulas):



So 3 x 1 1/2" pipes will have less head loss than a single 2" pipe. An efficient pool can be designed with smaller pipes, you just have do it properly. However, I agree with Richard that given a choice I would use multiple runs of 2" pipe vs 1 1/2" pipe.

Note too there is such a thing as too little head loss. Axial and radial thrust increases with flow rate so if the operating point is far to the right of the best efficiency point, the bearings won't last as long.

Thanks Richard - yes. In my case, I have separate 2" runs for each of 2 skimmers, a 2" run for the main drain, and a 1.5" run for the cleaner. But even if each run was 1.5", having multiple runs yields less head loss than a single larger pipe as Mark's chart demonstrates. From Mark's chart, my three 2" runs for skimmers and Main drain is equal to a single 3.04" pipe. The fact that I can adjust each individually at the pad is a huge convenience that I now realize not everyone has. It is only on this and other forums where I've seen and learned of many, many swimming pools with the main drain tied into the skimmer, and then a single run back to the pad.

But my point, Bruce, is that simply saying that a pool should be plumbed with 2" or 2.5" pipe is an oversimplification - one should look at the overall plumbing design rather than only the size of the pipe. It is possible the the OPs builder plans on multiple 1.5" runs, which may be just fine for the size of his pool and pump. Given 2 skimmers and a main drain, it would be the same as a single 2.28" pipe.

no-mas, I think we all agree that multiple runs are better than 1.

However, from the below chart (also from Mark's sticky) using 3 runs of 2.5" pipe instead of 1.5" pipe results in approximately half the head loss - that can add up to a really big difference! Just pulling numbers out of the air, if using 2.5 instead of 1.5 pipe gets you 20' less dynamic head (quite possible), you are looking at quite a difference in flow rate (that would depend on the pump).

No argument here.


I wish there were more builders like you out there!


Yeah, but I think, especially for those that are new, asking questions and learning, it is too often left unsaid.

Plumbing is not like a chain. It's not "only as strong as the weakest link." 2-1/2" plumbing with 1-1/2" fittings will flow better than 1-1/2" plumbing and fittings. Think of drinking a milk shake through a straw. The longer the straw, the harder it will be. Resistance is proportional to the length at the given diameter. Since the equipment fittings are only a couple of inches in length, they contribute very little to the restriction compared to the rest of the system. Besides, all the equipment I used had at least 2" fittings. In my shopping, I didn't see much with 1-1/2" fittings. And lastly, the pumps nowdays are a lot more efficient. They move a lot more water at the same hp. To keep them operating at their BEP, you need to accomodate for that. The equipment will last longer that way.

When the curse words come out, you know you started a good topic! (or restarted one) Btw, if there is no main drain does the conversation change at all? I can almost predict the debate about having or not having a main drain! While bidding, I ran into builders that use them and builders that don't. I noticed that a few folks mentioned them when discussing pipe size.

Finally, does increased flow mean that I would need to reconsider any of my other equipment (pump, filter, heater)? Can the greater flow wear out any of this equipment more quickly?

For main drains, ANSI/APSP-7 recommends the following:



In most places these are only recommendations for residential pools but I think some cities are now making these requirements as well. I believe anti-vortex drain covers are now mandatory in all regions.

So these requirements almost dictate that you have at least 2 1/2" pipe for the drain to drain connector pipe and 2" for the rest. For spas, I would definitely use at least 2 1/2" pipe and preferably 3" if for nothing else to get maximum flow rate for the jets.

For some reason, this thread reminds me of a photo I saw... A user in another forum was told that sweep 90s were more efficient than ells, so he demanded his plumber use as many sweeps as possible. He posted that several plumbers turned him down, but he finally one to plumb the way he wanted. Here is what he wound up with:



I'm not sure why I post this, since everyone here seems to agree that designing a plumbing system to minimize head loss is a good thing - me included. The pictured design certainly appears to be efficient. I guess it simply demonstrates that one can take the best of intentions too far.

That cracks me up every time I see it!! Looks like that "Octo-Guy" from the old Spiderman comics (yeah; I'm old!). I really love that 3 way Jandy "above" the heater

Could be better. I see a couple 90°s in there that aren't sweeps.

There is no question, 2" pipe is better. The improvement going from 1.5" to 2" pipe is not dramatic, but it is real. Since the cost to upgrade is very small, you get a lot of improvement per dollar spent.

no-mas, I think that is possibly the most awesome thing that I have seen on here yet.

I think I'd need two sharpies to label all those lines...holy cow!

FWIW, I have 2 " piping on my AG system. ARR ARRR ARRRR (in my best tim the tool man taylor impression)

Plumber cheated I see 16 regular 90's HAHAHA can Anyone find more?

This photo is recockulous The only thing that could trump this is if the guy had the plumber pipe it all with 1 1/2" spa-flex and straight couplers only. COuld you imagine the spagetti mess. She'd be smooth turns though