2" plumbing worth an extra $1k?

[BlueWRXPride]

I'm working with my installer on a new in-ground pool of 22,000 gallons. I am going to be using a 26" sand filter that takes 300 lbs of sand and a flow rate of 70gpm. The mechanicals will be around 30' from the nearest point on the pool. There are going to be 3 or 4 return jets, 2 skimmers, 2 floor drains, and 3 deck jets.

From what I've been reading on here, having 2" plumbing is always preferred, but in my region, the standard install uses 1.5" PVC. Basically because in this region, lowest cost wins in general, so the installers have learned to default to 1.5". I asked about using 2" instead, and they're happy to do it, for an additional $940. In the grand scheme of things it's not that much, but it's still $1k that I don't want to spend if I'm not going to benefit from it. Based on the information above, is there any way to tell if that $1k would be well spent? Or would it really not make a big difference in my case?

 

[JamesW]

As long as you keep the water velocity below 6 ft/sec on the suction and below 8 ft/sec on the pressure side of the pump, you should be fine.

• Size.......6 ft/sec......8 ft/sec.
• 1.5"...........38...............51 gpm
• 2"..............63...............84 gpm
• 2.5............90.............119 gpm
• 3.0".........138.............184 gpm

It's probably building code to follow these velocity rules anyway.

In any case, I would definitely not use anything less than 2" for pool suction.

2" pvc isn't that much more expensive than 1.5" pvc pipe and fittings.

I can understand some upcharge, but almost $1,000 more seems excessive.

 

[JamesW]

I highly recommend a variable speed pump.

Whatever you do, do not get a single speed pump.

The 26" filter is a 55 gpm filter, in my opinion.

Do you have any equipment or features that require more than 40 gpm?

 

[BlueWRXPride]

This is the pump that they are planning on using: Power Defender 165 Variable Speed – Waterway Plastics

There are no features other than the 3 deck jets i mentioned in my post.

 

[ksteber]

Strictly speaking in terms of volume and friction loss, I would strongly recommend going with the 2” piping. I agree that almost $1K is a bit pricey though.

 

[JamesW]

Ok. In any case, I would never use 1.5" pvc for suction.

Check your local building codes to see if the velocity rules are required.

If yes, educate the builder.

 

[BlueWRXPride]

I don't think I'd have much luck going back to them and saying I want the 2" piping, but give me a lower price, so I'm going to have to decide if it's worth it. I get there's no downside to larger pipes other than cost, I'm just not sure how tangible the benefit will be. Maybe I split the middle and leave the returns at 1.5" and do the suction side at 2".

Doesn't the answer depend on how the plumbing is done? Is it standard practice that all 4 suction lines are run independently back to the pump and then joined? Or could they be combined at the pool and then run as a single 1.5" back to the pump?

 

[mguzzy]

Part for Part the price is not that big of a difference. but if the builder has to order 2 inch pipe and fittings because he doesn't keep it in stock then there is extra man power involved.. so maybe it kinda justified.. I said kinda

edit: And hey.. wouldn't hurt to try? Say hey, This is the price difference when I priced the parts at home depot.. how about I split the difference with you? say $500 extra and see if he bites?

 

[BlueWRXPride]

Part for Part the price is not that big of a difference. but if the builder has to order 2 inch pipe and fittings because he doesn't keep it in stock then there is extra man power involved.. so maybe it kinda justified.. I said kinda

Eh, when I asked about the 2" plumbing he said they already stock all of it for when they need it with high flow water features...so that theory is out

 

[BlueWRXPride]

But it does include increasing the size of everything, valves, fittings, etc. Not just the tubing of course.

 

[JamesW]

I would not have much confidence in a pool builder who doesn't use 2" pvc on a regular basis.

Definitely do not tie the skimmers together underground.

Run a 2" line from each skimmer to the equipment pad.

The main drains need to be tied together and run as a single line. Run the line to the equipment pad and do not tie it into a skimmer.

 

[beegee226]

Ask him what the price for labor is and you'll provide the materials.

 

[BlueWRXPride]

He said it would be $620 to do just the suction side with 2". I'll probably consider that a middle ground and go with it.

 

[Rossterman]

Welcome to the world of change orders. They are free to charge anything they want unless your contract specifies method to determine modification costs. For example, language like “costs for changes to original bid specs will be determined at actual builders Out of pocket cost difference plus 20% mark up” Helps keep contractors honest

 

[sktn77a]

2" sch 40 PVC pipe and fittings is about 25% more expensive that 1.5". Can't speak to the additional cost of anything that it is attached to (the pump already has 2" unions). Get the 2" - you'll be glad you did down the road.

 

[BlueWRXPride]

So I get that 2" is better than 1.5", but why? What benefit will I actually see in my pool ownership? I know it keeps the flow rate lower, but what does that do? Make the pump work a little less hard?

 

[JamesW]

Here is the pump curve chart.

As you can see, the lower the head loss, the lower you can keep the speed for the same flow rate.

That means power savings.

For example, if you wanted 40 gpm of flow, the speed you would need to run depends on the total head loss at 40 gpm.

Head........rpm
11 ft........1,600
23 ft........2,100
40 ft........2,600
60 ft........3,100

The power used is (theoretically) increased/decreased by the ratio of ((speed 1) ÷ (speed 2))^3.

So, that's a big difference in power usage.

Doubling the speed uses about 8 times as much power as at the lower speed.

Actual results are closer to about six times or an exponent of about 2.6.

The power difference between 1,600 rpm and 2,600 rpm is about
((2,600) ÷ (1,600))^2.6 = 3.5
which is about 3.5 times as much power for the same amount of flow.

That's why I usually also recommend a big cartridge filter because it's less head loss.

 

[mguzzy]

So I get that 2" is better than 1.5", but why? What benefit will I actually see in my pool ownership? I know it keeps the flow rate lower, but what does that do? Make the pump work a little less hard?

That is a big, "It depends" kind of question. Depends on your features (which you listed) but what kind of jets are you using on the deck, design of the piping, etc for example. You may or may not see a discernible difference in your flow. But you want to err on the side of more flow. Because you can't add it back in once you commit to a smaller pipe size. I can't recount on the number of times I've read that someone can't turn on all their bells and whistles (Spa, water features, solar) becuase the system wasn't designed to accommodate it.

 

[jimmythegreek]

For a standard simple pool 1.5 for returns is normal. No reason to upsize unless stacking multiple returns on a single line. All the manifolds above ground should be 2" and so should the suction lines. You want 3 suction feeds to pump independently. Skimmer, skimmer, main drains. 600ish is fair for an upcharge with homeruns of a short distance. Most new equipment is 2" taps anyways nowadays. Shows that he doeant worry much about flow 2" is standard with us all sweeps and neverlube valves too dont use cheap ball valves. Buy online amd provide them if necessary