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Thread: Pump and plumbing questions

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    Join Date
    Jun 2014
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    Question Pump and plumbing questions

    9 years ago we replaced a leaking 1.5 HP "Hydramax II" pump with a Whisperflo 1HP dual speed. There were issues with the plumbing, including a leak, so much of that was redone as well. However, we had an issue that when we'd turn the pump off, the water level in the pump would immediately drop and it would lose its prime. The only way to prevent it was to quickly close all the valves to prevent the water drop. Should we have installed a check valve before the pump? I guess we had an air leak as well or perhaps it was the sticky skimmer weir, because running the pump long enough, we'd eventually get too much air in there and lose prime again.

    We just lived with these issues and now our Whisperflo died (it ran dry too often, I'm sure) and we want to make sure we correct the issue with this maintenance. One guy who came out took one look at the pump and said 1HP wasn't enough. He didn't seem to take into account the model of our pump, so we tended to discount this. However, our equipment is much higher than the pool and even more-so after our remodel 9 years ago, so we're wondering if this means we need a more powerful pump. We were hoping to use low speed most of the time to save power and ensure enough chlorination from our salt water chlorinator.

    It looks like pump sizing depends on a lot of factors, some of which I probably don't have the answers to right now! We have a pool with attached spa that holds around 35,000 gallons of water. There are 3 skimmers, a main pool drain, main spa drain and 2 returns (that run into the same pipe). All the pipes from the pool are 1.5" and the new plumbing (above ground to the pump and filter) are 2". I'd have to take a wild guess on feet of head. Many of the lines are buried. The pump is about 2-3' above the water level. I plan to go out there and try to get some actual measurements, but maybe this is a start? The filter is an FNS Plus 48.

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    JasonLion's Avatar
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    Re: Pump and plumbing questions

    Welcome to TFP!

    You old pump was a little too large, and while adequate, that filter is smaller than I would recommend for that pool.

    You clearly had (and presumably still have) a suction side air leak. Adding a check valve on the suction side plumbing down near the pool water level would certainly help things, but that is not a substitute for fixing the air leak.
    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: Pump and plumbing questions

    Quote Originally Posted by JasonLion View Post
    Welcome to TFP!

    You old pump was a little too large, and while adequate, that filter is smaller than I would recommend for that pool.

    You clearly had (and presumably still have) a suction side air leak. Adding a check valve on the suction side plumbing down near the pool water level would certainly help things, but that is not a substitute for fixing the air leak.
    Thanks for the welcome! So it sounds like you're saying the Whisperflo 1HP should be fine. We were considering replacing it with a 1.5HP because the 1HP dual speed seems to be 115v now and our old one is 230v. The guy that came out and said 1HP wasn't enough also told us we shouldn't bother with a dual speed pump. Should we be avoiding him? Actually, the pump was running, although very loudly, until he came out and then did something to it and it went POP and is now completely dead. So, there have been a few red flags...

    I guess we'll be sticking with the filter for now, since that seems to be ok for the most part. You'd recommend an FNS 60? That's the only thing I saw larger in that model. The flow rate on the 48 seemed plenty at the time. Back when we did all this work, we had the pool pressure tested. You can tell I'm a novice, because of this question - did that only check for water leaks and not air leaks? How does one go about finding an air leak? Another novice question - if we did want to install a check valve down near the pool level, wouldn't we have to install one on each line individually? Not much comes together until right at the pump, which is why I was wondering if one should go there. I have a feeling I'll be taking a photo of our setup, because that may be an issue too.

    We have another company coming out Friday and perhaps they'll be more helpful. We had a big name company come out a few weeks ago and they ignored all the mechanical issues and just tried to sell us a pool coating for $12k. Why would we want a $12k coating on a pool that doesn't run?

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    JasonLion's Avatar
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    Re: Pump and plumbing questions

    A 1 HP Whisperflo is too much. Getting an even larger pump would just waste electricity. There are various pumps that are more appropriate and work with 230 volts. A SuperFlo 1 HP 2 speed, SF-N2-1A, runs on 230 volts and will save on electrical costs.

    Yes, avoid the person who has been telling you these mistaken things.

    There is an article in the Solving Problems section of Pool School on finding suction side air leaks.
    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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