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Thread: Suction side air leak/failure of pump to prime

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    Suction side air leak/failure of pump to prime

    I am very happy to find this website. I have had a pool service for the past 6 years and never really took the time to learn enough about my pool. In an effort to save on costs and teach my sons how to take care of the pool I have recently been studying what I need to learn about the pool so we can take care of it ourselves. Recently I discovered a fair amount of air in the pump basket and failure of the pump to prime when it starts up in the morning or after I shut down the pump to clean the pump basket. This is concerning to me as twice now I have found the pump getting very hot because it was not pulling enough water into the basket. I have read some forums and pool school to try to solve the problem. The gasket on lid looks good but I used silicone on it anyway and also checked the suction side pump drain plug and used silicone on it as well. Water level in pool is good. I thought it might be the check valve so replaced it but still having the problem. I have tried the "water trick" mentioned in pool school using a hose to run water over the suction side valves and joints but it didn't help either. I think the problem may be coming from a sensor line that feeds into the main drain line as it comes out of the ground and prior to going into the pump. I have a fairly automated pool and I think this is either the sensor line for pH or ORP. In any event, the place it enters the PVC seems to have a small worn gasket. I have applied silicone around it and it may have helped a little to decrease the air bubbles but they are still significant and the pump still failed to prime on restart. Is there a place online that I could by a new gasket for this black rubber hose/sensor line into the PVC and it would show me how to replace it? If this isn't the problem I am afraid it may be a problem with the pipes underground. Does anyone have any suggestions or advice for this problem? Thanks in advance for any help.
    Built 11/2009; 16x25 IG free form with raised spa and spillover; 10,500 gal; gunite color quartz plaster finish; flagstone coping; travertine deck; Hayward NorthStar 2.5HP pump; U.S. motors 2HP motor; Hayward 525sf Swimclear cartridge filter; Autopilot salt chlorine generator; Autopilot pool chemistry controller; Polaris 3900 sport pool cleaner; Polaris PB4-60 pool cleaner motor(booster pump); Hayward 400K BTU heater, TF-100 test kit

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    Texas Splash's Avatar
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    Re: Suction side air leak/failure of pump to prime

    So you have both a main drain and skimmer. Have you tried isolating suction to the pump from just one source (skimmer or drain) at a time to try and isolate the possible source of the air suction leak?
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
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    Mod Squad pooldv's Avatar
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    Re: Suction side air leak/failure of pump to prime

    Most sensors that are installed into plumbing lines use o-rings that should be available at a pool store.
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    Re: Suction side air leak/failure of pump to prime

    Okay, thanks. I will check that out.
    Built 11/2009; 16x25 IG free form with raised spa and spillover; 10,500 gal; gunite color quartz plaster finish; flagstone coping; travertine deck; Hayward NorthStar 2.5HP pump; U.S. motors 2HP motor; Hayward 525sf Swimclear cartridge filter; Autopilot salt chlorine generator; Autopilot pool chemistry controller; Polaris 3900 sport pool cleaner; Polaris PB4-60 pool cleaner motor(booster pump); Hayward 400K BTU heater, TF-100 test kit

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    Re: Suction side air leak/failure of pump to prime

    Thanks. I turned the valve to close off the main drain (which the sensor is connected to) and it does reduce the air bubbles a little. When I close off the skimmer and have all suction from the main drain there is a lot of air so I think the main leak is in this line, probable from the sensor o-ring. There is still some air in the basket when i close the main drain off. Could this still be coming from the main drain line with seepage of air around the valve even though I have it closed off (i.e. are these valves sometimes not air tight within the PVC?). Would an air leak such as this cause failure to prime or would it just cause air bubbles? Thanks again for your help. Excellent idea!
    Built 11/2009; 16x25 IG free form with raised spa and spillover; 10,500 gal; gunite color quartz plaster finish; flagstone coping; travertine deck; Hayward NorthStar 2.5HP pump; U.S. motors 2HP motor; Hayward 525sf Swimclear cartridge filter; Autopilot salt chlorine generator; Autopilot pool chemistry controller; Polaris 3900 sport pool cleaner; Polaris PB4-60 pool cleaner motor(booster pump); Hayward 400K BTU heater, TF-100 test kit

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    Mod Squad pooldv's Avatar
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    Re: Suction side air leak/failure of pump to prime

    Is it a Jandy valve? They are usually airtight. The internal mechanism can be replaced. But if new in 2009 it should be fine. If it is a ball valve then it is possible that it leaks. Yes, that could impact the pump priming if there is enough of an air leak.
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    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

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    Re: Suction side air leak/failure of pump to prime

    IMG_1031.jpg

    Looks like it is a Hayward Valve PSV? For some reason this website is flipping the picture sideways when I upload it. The picture shows the label on the backside of the valve and the sensor into the PVC that I think is causing the leak is to the left (should be below valve if the picture was oriented correctly).Thanks.
    Built 11/2009; 16x25 IG free form with raised spa and spillover; 10,500 gal; gunite color quartz plaster finish; flagstone coping; travertine deck; Hayward NorthStar 2.5HP pump; U.S. motors 2HP motor; Hayward 525sf Swimclear cartridge filter; Autopilot salt chlorine generator; Autopilot pool chemistry controller; Polaris 3900 sport pool cleaner; Polaris PB4-60 pool cleaner motor(booster pump); Hayward 400K BTU heater, TF-100 test kit

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    Re: Suction side air leak/failure of pump to prime

    Your question ...Would an air leak such as this cause failure to prime or would it just cause air bubbles? Yes it would cause the pump basket to eventually fill with air when not running and therefor lose its prime.

    I had a difficult one to find also. I used the shaving cream method and the water hose method and could not locate the air leak. I decided to build temporary coffer dams (or little ponds) around the sections of pipe from the ground to the intake side of the pump in sections. I used something like an 8 mil poly and duck tape. It was not pretty and it will leak but the water hose flow can make up for the leaking. I found it at the pump intake threaded pipe fitting. I had to make that coffer dam around the pump housing only (not the motor). I was certain it was the o-ring on the cover ... I made the dam higher than the pump basket cover.

    When I filled the "leaky" section dam with water the bubbles stopped and the basket filled with water to the top. I shut off the water and let the leaky dam drain ... when it got down to the threaded connection the air bubbles appeared again. Filled it back up and the air bubbles went away. Replaced the threaded connection with a threaded union that has an additional o-ring that fits against the pump housing.
    20,000 gal, 18 x 36 IG Vinyl, 1.5 HP Hayward 2610x152S two speed, Sta-Rite S870 sand filter, Raypak 265,000 BTU P-R26A-EP-C, TF-100 Test Kit

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    Agent99's Avatar
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    Re: Suction side air leak/failure of pump to prime

    OldPoolBoy2,

    I think most of the threads on pump bodies (typically 2") are actually STRAIGHT threads and not tapered like a pipe nipple. I think a lot of the literature out there incorrectly states that the pump is 2" (or whatever) NPT when it fact, it is not.

    I called Pentair and asked their technical department this very question and it was confirmed that the threads are straight. He couldn't explain why most of the literature out there claimed NPT and seemed surprised by what I told him.

    If you look at the unions available for pool pumps, you will see that most of them have an external o-ring that seals against the pump body. This is a big clue that the threads are straight and not tapered. Straight threads need the extra seal but tapered would not.

    The issue is that a 2" NPT fits just fine in 2" straight. It may even seal just fine (mine did with pipe dope) but then again, it may leak. I have a PVC pipe nipple threaded into my IntelliFlo pump but I did buy the unions (just arrived yesterday) and will redo the pump one day. Since mine isn't leaking, I'm not in a hurry but it is on the list.
    ----Chris----
    25k IG/Spa Figure 8, 18x36, Pebble Sheen Blue Granite, Sta-Rite S8M150 Cartridge Filter, Pentair 460805 400k BTU Heater & 011018 IntelliFlo VarSpd
    Liquidator, Fafco Solar Heat, Polaris PB460 Booster Pump w/280 cleaner, Katchaleaf Cover, TF100 Test Kit, FAKE MAIN DRAIN

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    Re: Suction side air leak/failure of pump to prime

    Thanks, I appreciate the tip!
    Built 11/2009; 16x25 IG free form with raised spa and spillover; 10,500 gal; gunite color quartz plaster finish; flagstone coping; travertine deck; Hayward NorthStar 2.5HP pump; U.S. motors 2HP motor; Hayward 525sf Swimclear cartridge filter; Autopilot salt chlorine generator; Autopilot pool chemistry controller; Polaris 3900 sport pool cleaner; Polaris PB4-60 pool cleaner motor(booster pump); Hayward 400K BTU heater, TF-100 test kit

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