Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 7 of 7

Thread: 1.5" vs 2" piping, high but not high enough flow rates

  1. Back To Top    #1

    In the Industry

    Join Date
    Jun 2010
    Posts
    74

    1.5" vs 2" piping, high but not high enough flow rates

    So here's my story. Please bear with me. To visualize it better, I've put photos of the equipment room on Imgur at http://imgur.com/a/W0N3p rather than attach them to this post (for which I would have to reduce the photo resolution). Click the gear icon in the top corner of each photo to view it at full resolution.

    I've got this pool that I just started taking care of this year. I walked into it being told that a new filter head was required; I ordered the current model to replace the old one (no longer available) without really looking at the overall setup. They also had a flow meter mounted just above the pump, without anywhere near the required pipe length around it, so while replacing the head I also rebuilt that portion of pipe.

    What I failed to notice is that the filter head on this Hayward S-310T filter had 1.5" ports, where the entire rest of the system - intakes, pump, heater, and output - had 2" piping (or larger). At some point in the past, someone installed this filter head with 1.5" ports, and a 1.5" pipe from there, to the heater, and back out to the chlorine feeder. This seems to be causing quite a restriction. Unfortunately, replacing the head with a 2" version and rebuilding all the pipes isn't really an option now; the connection inside the filter was so tight that I had to pound it into place with a hammer and a block of wood. I doubt I could get it off without wrecking the pipe inside the filter.

    This is a nearly 200,000L pool by my best estimates. (I plan to do an alkalinity change test to get a better idea of the volume.) The system is currently moving around 230 LPM - a 14.5 hour turnover rate. Health regulations here require a maximum of 12 hours, with 8 hours preferred. Here's the kicker. If I open the Heater Bypass valve (in addition to leaving the heater open, of course), the flow rate jumps up to 275 LPM, which gives us very nearly a 12 hour turnover rate. In addition, the filter pressure drops from ~150kPa down to ~110kPa.

    So here are my questions. I'd like to get the higher flow rate, especially since I've already had a couple of clarity issues in the first month. The filter specifies an operating flow rate much much higher than what we've got, but that number probably assumed a filter head with 2" ports - is it okay to push that much water through the smaller filter head, or is there a chance of it causing damage or wrecking the gasket? What about the existing 1.5" piping - can I safely leave it (especially the chunk of black spa hose) with that high of a flow rate? The water velocity in some parts of the piping would be over 13 ft/second - way above the recommended specs for PVC that I've seen. What about leaving the 1.5" filter head, but replacing all the piping with 2"? (and on that note - the Hayward chlorine feeder originally had 2" connections, but the "pipe" through the bottom of it restricts to less than 1.5"...if I replace the rest with 2", is this going to still have a restriction?)
    * Responsible for the operation of 21 semi-private pools and spas at 11 locations, varying from 1,900L to 20,000L spas and from 13,000L to 200,000L pools.

  2. Back To Top    #2
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: 1.5" vs 2" piping, high but not high enough flow rates

    Short segments of 1.5" pipe do not cause significant flow restrictions. Long sections will cause some flow restriction, in proportion to the length of the segment. Longer runs of 1.5" cause more restriction, but it takes quite a bit of 1.5" pipe before that becomes significant enough to be noticeable. Six to ten feet of 1.5" pipe plus a few 1/5" fittings will not cause flow rate differences that matter in this situation. Replacing the entire multi-port valve with a hi-flow 2" equivalent would improve things, but not all that much, not as much as bypassing the heater.

    Higher flow rates through PVC/poly pipe are not a problem other than wasting a little electricity. Metal pipe can be damaged by high flow rates, but not plastic.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  3. Back To Top    #3
    Isaac-1's Avatar
    Join Date
    May 2010
    Location
    SW Louisiana
    Posts
    6,711

    Re: 1.5" vs 2" piping, high but not high enough flow rates

    I don't see any easy quick fixes to your problem, cheapest option I can think of that might work if you have room is add a second filter parallel to the primary filter that bypasses the heater, perhaps a cartridge filter of some type.

    Ike

    p.s. don't worry about higher flow rates in PVC unless they are WAY about the general engineering suggestion, many of those seem to be based on very outdated concepts before people knew how PVC would stand up to real world use since these would be easy to replace if the extra flow causes them to wear out if a few decades.
    Indoor 20x40 35,000 gallon vinyl pool with 1.5 HP 2 speed Jandy FloPro pump, Hayward EC75 Perflex DE filter, 11 4x12 Techno-Solis solar panels w/ Aquasolar controller, Aquabot Turbo T Robot Cleaner. Also LMI metering chlorine dispenser pump and HotSpring Jetsetter
    I use and endorse TFtestKits TF-100 from http://tftestkits.net
    ~Remember TFP counts on your donations to keep this site ad free~

  4. Back To Top    #4
    mas985's Avatar
    Join Date
    May 2007
    Location
    Pleasanton, CA
    Posts
    11,482

    Re: 1.5" vs 2" piping, high but not high enough flow rates

    I don't think replacing just the 1.5" pipe is going to compensate for the heater head loss.

    If I open the Heater Bypass valve (in addition to leaving the heater open, of course), the flow rate jumps up to 275 LPM, which gives us very nearly a 12 hour turnover rate. In addition, the filter pressure drops from ~150kPa down to ~110kPa.
    Why can't you just run that way all the time? Even with the bypass open, the heater should be getting enough flow rate/pressure to operate.

    If you need to bump up the flow rate further, I would look into replacing the multi-port valve with a 2". Most valves have quite a bit of head loss and the difference between a 1.5" and a 2" valve is about the same as a typical heater. But combining that with the heater bypass should give you plenty of margin.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

  5. Back To Top    #5

    In the Industry

    Join Date
    Jun 2010
    Posts
    74

    Re: 1.5" vs 2" piping, high but not high enough flow rates

    Alright. I think I'm mostly concerned about the piece of spa hose now. It goes absolutely nuts when I open the heater bypass (due to the flow increase), and I worry that my glue job won't hold.
    * Responsible for the operation of 21 semi-private pools and spas at 11 locations, varying from 1,900L to 20,000L spas and from 13,000L to 200,000L pools.

  6. Back To Top    #6
    mas985's Avatar
    Join Date
    May 2007
    Location
    Pleasanton, CA
    Posts
    11,482

    Re: 1.5" vs 2" piping, high but not high enough flow rates

    That kind of flex is not really designed for high flow rates so do yourself a favor and replace it before it breaks.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

  7. Back To Top    #7

    In the Industry

    Join Date
    Jun 2010
    Posts
    74

    Re: 1.5" vs 2" piping, high but not high enough flow rates

    What about the white spa hose? Less flexible. The alignment between the two ends will be tricky to do with straight PVC.
    * Responsible for the operation of 21 semi-private pools and spas at 11 locations, varying from 1,900L to 20,000L spas and from 13,000L to 200,000L pools.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •