Pump Size and Code Requirements for Plumbing

[darinclifton]

So question about the IRC/ISPRC 311.3 "The water velocity in the return lines shall not exceed 8 feet per second". Does anyone have experience on the impacts of modern variable speed pumps and flow requirements. For example the Intelliflow XF supports up to 3" connections, but at a with modest head loss of 30' (actual design) at top rated speed 200gpm (~8.5 f/sec) would exceed the allowable flowrate for 3" plumbing. Going to 4" plumbing would solve this problem but the suction/return velocity at the pump would still exceed the maximum "Code Requirement" because of the connection size. Even the new Intelliflow 3 at full speed would exceed the 6 f/sec on the suction side.

It is fairly easy to control the flow rate at an individual suction or return but not as easy to control the maximum flow that is limited by the actual pump design connections. Considering that most pools are plumbed with 1 1/2" and 2" lines, Even using Pentair Intelliflow i1 with 45' of head can hit 90gpm (~9 f/sec) not sure how to interpret this.

It is kinda funny that the code requires the use of Variable Speed Flow pumps, but there are few VSF pumps on the market that will satisfy the code velocity requirements unless you have a bad hydraulic design. The code is pretty clear so I am not sure what I am missing here ....

Thanks!

 

[JamesW]

Most inspectors are not going to worry about the final reduction at the pump.​

As long as the main plumbing is compliant, I do not think that most inspectors will be worried that the pipe reduces down from 4" to 3" at the pump.

In any case, always verify with the actual inspector to be sure as they might interpret the rules any way they want.

Pipe Size and Flow Rates.​

You want to keep the water velocity below 6 ft/sec on the suction and below 8 ft/sec on the pressure side of the pump.[7]

Pipe Size	6 ft/sec	8 ft/sec
1.5"	38 GPM	51 GPM
2"	63 GPM	84 GPM
2.5	90 GPM	119 GPM
3.0"	138 GPM	184 GPM
4.0"	235 GPM	312 GPM

 

[1poolman1]

So question about the IRC/ISPRC 311.3 "The water velocity in the return lines shall not exceed 8 feet per second". Does anyone have experience on the impacts of modern variable speed pumps and flow requirements. For example the Intelliflow XF supports up to 3" connections, but at a with modest head loss of 30' (actual design) at top rated speed 200gpm (~8.5 f/sec) would exceed the allowable flowrate for 3" plumbing. Going to 4" plumbing would solve this problem but the suction/return velocity at the pump would still exceed the maximum "Code Requirement" because of the connection size. Even the new Intelliflow 3 at full speed would exceed the 6 f/sec on the suction side.

It is fairly easy to control the flow rate at an individual suction or return but not as easy to control the maximum flow that is limited by the actual pump design connections. Considering that most pools are plumbed with 1 1/2" and 2" lines, Even using Pentair Intelliflow i1 with 45' of head can hit 90gpm (~9 f/sec) not sure how to interpret this.

It is kinda funny that the code requires the use of Variable Speed Flow pumps, but there are few VSF pumps on the market that will satisfy the code velocity requirements unless you have a bad hydraulic design. The code is pretty clear so I am not sure what I am missing here ....

Thanks!

Your post illustrates one advantage of a VSP, you control the flow, not that anyone really cares other than your energy bill, your filter, your pool cleaner, your SWG, your spa jets, your water features. Those flow rates are more for VGB regulations and on a commercial pool would, likely, be enforced. They are around here, every commercial pool must have a working flow meter and the flow must meet the requirements of local code.

 

[darinclifton]

Your post illustrates one advantage of a VSP, you control the flow, not that anyone really cares other than your energy bill, your filter, your pool cleaner, your SWG, your spa jets, your water features. Those flow rates are more for VGB regulations and on a commercial pool would, likely, be enforced. They are around here, every commercial pool must have a working flow meter and the flow must meet the requirements of local code.

The VSF pump is not a commercial / residential issue. Per DOE rule, after July 2020 manufactures are not allowed to manufacture / distribute swimming pool pumps over 1hp that are not Variable Speed Flow pump. The point of my post is that I can't find anywhere in the code that allows for water speeds greater than 8 f/sec in residential pool plumbing systems.

Personally the way they have written the code is fairly stupid. I am not certain what the point is of the flow of the water in a pipe some distance away (for safety) from an outlet is. I 100% get entrapment and APSP-7 \4.6.2 has reasonable requirements for flow ratings at covers and grates. I think that the code makes the assumption that every outlet is plumbed directly to the pad with no other plumbing considerations. APSP-7 actually limits the flow at on outlet to 3 f/sec at the outlet

I am a design professional and don't get the "option" to not read the code literally, so when I see the specifications for a pump and see the designed attachments and look at the table for allowable flows based on that connection and they don't jive... well that is a head scratcher. My only conclusicon is that there is an assumption that all pools will suffer from bad hydraulic design. As a designer you can't rely on that someone will not turn the pump all the way and pull water from a single pipe (AKA stupid people do stupid things)

 

[JamesW]

Deleted.

 

[darinclifton]

From what?

Sorry, I was being facetious in that if the pools plumbing design is bad enough to raise the total pump head required, it would reduce the pumps efficiency enough to be code compliant.

 

[JamesW]

I am a design professional

Do you design pools?

 

[darinclifton]

Do you design pools?

Not specifically, but I am a licensed Architect.