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Thread: Liquidator and variable speed pumps

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    Liquidator and variable speed pumps

    I've read that the LQ can be finicky with variable speed pumps. Besides removing check valves, are there any other hints to make the two work properly together?
    Owner built 32,000g Diamond Brite IGP with 1,300g spa, Jandy 2.0hp ePump, DEV60 filter, LXi 400k btu NG heater, PS-8 control, QT 1.5hp blower, WaterColors, Liquidator, PoolBlaster, Blue Diamond

    Lehigh Custom Pools

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    JasonLion's Avatar
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    Re: Liquidator and variable speed pumps

    There are two primary problems with the LQ and a variable speed pump. First, when the pump is running on low speed there is very little pressure difference, which the LQ depends on. Second, If you are varying the pump speed over the course of a normal day the LQ flow rate will vary dramatically at different pump speeds, which can sometimes make the LQ difficult to calibrate.

    There are various changes you can make to the LQ to help with the low pressure difference issue. LQ 3/8 line conversion (How to increase flow) talks about one of the more complex and more successful modifications.
    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

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    Re: Liquidator and variable speed pumps

    Jason...

    That's pretty much what I had expected. I'll be doing the hose conversion to take care of flow issues.

    As for speed/pressure variations during the day, my plan is to run at priming speed for an hour, then low speed for the rest of the day. That first hour will be higher FC flow, so I'll do that before swimming hours, then the remainder of the day will be 'under-flowed' to compensate. Since this schedule would be followed daily, FC variation would be minimal.

    Question though. The main reason for buying a variable speed pump is to run low for normal filtration, then push hard for spa use. Could I selectively plumb the LQ to pool suction/pressure only so when I'm running the spa, we don't get bleached? This would require the suction line to be plumbed pre actuated inlet valve...and the pressure line to be plumbed post actuated return. This isn't the recommended location, think it would be an issue?

    As an alternative, if I close off the lines from the LQ with a solenoid, I assume I could trigger the LQ to chlorinate in a particular time window while the pump is running at a higher speed and do a heavy timed dose, then close it off for the remainder of the day.
    Owner built 32,000g Diamond Brite IGP with 1,300g spa, Jandy 2.0hp ePump, DEV60 filter, LXi 400k btu NG heater, PS-8 control, QT 1.5hp blower, WaterColors, Liquidator, PoolBlaster, Blue Diamond

    Lehigh Custom Pools

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    JasonLion's Avatar
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    Re: Liquidator and variable speed pumps

    Plumbing the LQ on the pool suction and return lines is a good idea. That should work just fine.

    For the different speeds at different times thing, as long as you use the same pattern of speeds for the same period of time each day you will be fine. Taking the spa out of consideration will make this much simpler.

    If you are going to run on a fairly high speed for an hour each day, it would be best if that was in the early evening. It doesn't make a huge difference, but it is more efficient to have higher FC levels overnight, when less chlorine is getting lost to sunlight.

    The solenoid idea is interesting, but I think you will find it difficult to get a solenoid controlled valve which can hold up to the concentrations of chlorine that occur in the LQ lines.
    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

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    Re: Liquidator and variable speed pumps

    I found a solenoid for corrosives...but at $750.00, maybe I'll stay simple...

    ...but the engineer in me is wondering about alternatives. I remember seeing a simple servo used to pinch silicone tubing to turn on/off a homemade liquid fish food feeder...

    Owner built 32,000g Diamond Brite IGP with 1,300g spa, Jandy 2.0hp ePump, DEV60 filter, LXi 400k btu NG heater, PS-8 control, QT 1.5hp blower, WaterColors, Liquidator, PoolBlaster, Blue Diamond

    Lehigh Custom Pools

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    Re: Liquidator and variable speed pumps

    One more question on this...

    I don't have any plain pipe between where my skimmers/drain are tee'd and the actuated valve.

    Skimmer/Drain tee -> EL -> Actuated valve -> pipe

    Could I tap into the el for the suction line or should I just pick the drain or skimmer pipe to tap?
    Owner built 32,000g Diamond Brite IGP with 1,300g spa, Jandy 2.0hp ePump, DEV60 filter, LXi 400k btu NG heater, PS-8 control, QT 1.5hp blower, WaterColors, Liquidator, PoolBlaster, Blue Diamond

    Lehigh Custom Pools

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    Join Date
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    Prosper, Texas
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    Re: Liquidator and variable speed pumps

    I know this is an old thread but I'm considering the liquidator and have some of these same concerns. I have a variable speed pump and typically run it at 45% from 7:30am - 10pm. I have it set to kick up to 75% from 1-2:30 when my cleaner and cleaner pump kick in.

    Now the spa is elevated and I will sometimes run the pump at 90% to get a nice full even waterfall when we have guest over or we are outside. Also it runs at 90% when heating the pool. Lastly spa mode runs the pump at 100%.

    So based on all this should I even consider the liquidator? Also for people using pucks or swg don't they run into these same issues if they have a variable speed pump? Maybe those are not as fast to create chlorine as flow from the liquidator would, not sure?

    Lastly any comments from variable speed pump and liquidator owners would be great.
    21,000 gallon pool w/spa, Pebble Sheen, Hayward EcoStar variable speed filter pump, Hayward DE6020 Filter, Hayward 400FDN Heater, Stenner pump with 15 gallon tank, Clear O3 ozone system, Hayward Goldline PS-8 controller, Hayward 6060 cleaner pump, Polaris 280 cleaner, Hayward EcoStar variable speed water feature pump.

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    Mod Squad Bama Rambler's Avatar
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    Re: Liquidator and variable speed pumps

    I don't own a variable speed pump but I can tell you that they work best with a steady suction head.

    You could in theory, make it work for you if you ran the pump on the same schedule every day. That way you could adjust the LQ flow so that it'd add enough FC to handle your daily need. Yeah, it'd overshoot some when running on high and it'd undershoot some when running on low but the daily average could be achieved. This is provided you run the system long enough with enough suction head so that it is able to deliver the required amount of FC per day.

    A better choice for you would be an injection pump. It adds a set amount of FC regardless of the main pump setting. I suggest running it on a separate timer from the main pump. That way if you decide to run the main pump outside it's normal schedule it won't affect the amount of FC added.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: Liquidator and variable speed pumps

    I agree with Bama. I tried the Liquidator and a variable speed pump. I tried many different configurations and could never get consistent CL flows. I have a single variable speed pump, no spa but do have a water feature that spills into the pool and a bubbler in the sunshelf. The pump is kicked up to a higher speed when using the water features and for skimming. This would result in over chlorination when the my kids and their friends were in the pool all day. I could never get the right amount of flow for my pool on low-speed where I run at for most of the day and was having to increase my high-speed run time. This defeats one of the purposes of a variable or two-speed pump.

    I went with a Stenner pump and it has worked perfectly. I use an extra relay from my Easytouch system to inject 3 times a day. I had planned to use a separate timer, but figured out a way to use my existing system. I have found the chlorine level to be very stable and is completely independent of pump speed or run time.
    22k gal, gunite, Pebblesheen, fountain/waterfall, no spa, Quad 100DE, Easytouch4, Pentair VS3050, Polaris 280, TFP-100 kit, Stenner pump

  10. Back To Top    #10

    Re: Liquidator and variable speed pumps

    Forgot to add. I have a 15gallon tank. I was able to go on a 10 day vacation this summer and did not have to ask anybody to add bleach. I can probably go a little longer, since Walmart and HEB bleach is now 8.25% vs 6%. Last summer I left for 10 days and the Liquidator decided for some reason not flow the same amount of bleach and I came home to a pool that was starting to turn green.
    22k gal, gunite, Pebblesheen, fountain/waterfall, no spa, Quad 100DE, Easytouch4, Pentair VS3050, Polaris 280, TFP-100 kit, Stenner pump

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    Join Date
    Dec 2011
    Location
    Prosper, Texas
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    Re: Liquidator and variable speed pumps

    Thanks guys I'll look into the stenner pump options and various post on here as I have several questions about them but don't want to derail this thread. Thanks.
    21,000 gallon pool w/spa, Pebble Sheen, Hayward EcoStar variable speed filter pump, Hayward DE6020 Filter, Hayward 400FDN Heater, Stenner pump with 15 gallon tank, Clear O3 ozone system, Hayward Goldline PS-8 controller, Hayward 6060 cleaner pump, Polaris 280 cleaner, Hayward EcoStar variable speed water feature pump.

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