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Thread: air bubbles in return lines and MD not working, help!

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    air bubbles in return lines and MD not working, help!

    I finally got my new de filter installed yesterday. I ran the filter over night and already i could see a difference. My question is the pump (1.5 HP) is working fine until I use my cleaner(Hayward nav) I connect the vacuum hose to my skimmer and it begins vacuuming in the pool. I noticed shortly after air bubbles in the return lines. This only happens when I connect the vacuum. twice now, Ive left the vacuum do its thing only to come back and find it floating and the pump running dry.

    what could be the cause of this? we just bought the house and inherited a 18k gunite pool. the new filter i got is a pentair de 48. Ive had to backwash three times already in 2 days.

    I also dove down because my pool has never had a main drain cover. with the pump running I dove down to check the Main drain and put my hand directly over it and absolutely felt no suction.

    are these two problems related?

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    Mod Squad Bama Rambler's Avatar
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    Re: air bubbles in return lines and MD not working, help!

    Normally the vacuum increases the negative head pressure on the pump suction when it's hooked up. What that amounts to is that you have a suction leak when you have the vacuum hooked up. It could at the pump basket housing cover. Did you lube the o-ring on the lid when you installed the pump? If you have any unions on the suction side you should lube those o-rings too.

    I don't think one problem has to do with the other, but I'll never say never.
    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
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    Richard320's Avatar
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    Re: air bubbles in return lines and MD not working, help!

    I get the same thing. My pump pushes the water out of the filter faster than it can suck it up through the vacuum hose. Pressure drops, outlets slow, and there is air in the pump basket. And eventually, air in the returns. Opening the spa drain a little keeps the basket full. I haven't done it enough to tell if it vacuums better or worse without the spa water. I do have to open the air bleed when I'm done, and then everything returns to normal.

    The lack of suction at the main drain is another problem I had. I was missing the diverterinside the skimmer. It goes under the basket. A flap on the bottom allows you to regulate the flow from above. Fully closed = no skimmer. Fully open = no main drain. It's trial-and-error getting it set for your pool. I bought mine for about ten bucks at the pool store, they had a bunch on the shelf.

    The fact that I was missing one and had no circulation at the bottom of the pool was just more proof that the pool service was useless.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: air bubbles in return lines and MD not working, help!

    Quote Originally Posted by Richard320
    I get the same thing. My pump pushes the water out of the filter faster than it can suck it up through the vacuum hose. Pressure drops, outlets slow, and there is air in the pump basket. And eventually, air in the returns. Opening the spa drain a little keeps the basket full. I haven't done it enough to tell if it vacuums better or worse without the spa water. I do have to open the air bleed when I'm done, and then everything returns to normal.

    The lack of suction at the main drain is another problem I had. I was missing the diverterinside the skimmer. It goes under the basket. A flap on the bottom allows you to regulate the flow from above. Fully closed = no skimmer. Fully open = no main drain. It's trial-and-error getting it set for your pool. I bought mine for about ten bucks at the pool store, they had a bunch on the shelf.

    The fact that I was missing one and had no circulation at the bottom of the pool was just more proof that the pool service was useless.
    hmmm I dont have a diverter at all. how do i install it? and how does not having this affect the suction of the main drain? thanks

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    Richard320's Avatar
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    Re: air bubbles in return lines and MD not working, help!

    Quote Originally Posted by heyitsme06
    hmmm I dont have a diverter at all. how do i install it? and how does not having this affect the suction of the main drain? thanks
    Look down inside the skimmer, with the basket out. There are probably two holes. One will be sucking water with the filter on. The other leads down to the main drain. If you do have the two holes, go buy a diverter, close the flap halfway or so, and drop it in. Put the basket back, and close the lid.

    I knew mine was working when I swept some small debris in and it got sucked away. You can also tell if you have a temperature gauge on the heater. Temp dropped 2 degrees within about a minute of installing the diverter. That told me it was pulling colder water from the depths. You can also tell by closing the flap on the diverter completely and dropping it in. There will be hardly any movement in the skimmer, yet plenty of water coming out the returns.

    You'll get to experiment to get the flap position right. What I've done is hold the weir (the skimmer flapper) closed and see how much turbulence is inside the skimmer. Then adjust the flapper so it looks about half as violent when you repeat the test with the diverter inside.

    It's all just experimentation, really.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: air bubbles in return lines and MD not working, help!

    well i found the diverter lying around in the pool stuff shed...





    your right there are two holes and I will try that asap. how does the diverter work to where it makes the main drain suck water? I would like to know how this works. and whats the best way to check if it works? dive down and check?

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    Re: air bubbles in return lines and MD not working, help!

    one more question, is there a way to connect my cleaner and still have the main drain sucking water? how can i connect the cleaner hose to the skimmer with the diverter in?

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    mas985's Avatar
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    Re: air bubbles in return lines and MD not working, help!

    Quote Originally Posted by heyitsme06
    your right there are two holes and I will try that asap. how does the diverter work to where it makes the main drain suck water? I would like to know how this works. and whats the best way to check if it works? dive down and check?
    The diverter/float restricts the flow of water through the skimmer path. This in turn decreases the pressure underneath the diverter so water is then sucked up through the main drain port and out the skimmer. Without it, the pressure on the main drain port is nearly zero so no water will flow out of the main drain port. Even having the diverter flap completely open will still draw some from the MD port. In fact, I took the flaps off my diverters/floats for both skimmers and the MD still has decent flow rate. Really, you don't need much from the MD anyway. It is just to keep the bottom circulated which the returns help with.

    As for the cleaner, if you use a cleaner plate attachment for the skimmer, then that will take the place of the diverter and so there will be some flow rate through the MD.
    Mark
    Hydraulics 101; Pump Ed 101; Pump and Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater, ThePoolCleaner

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