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Thread: Closing Pool - Blowing out main drain

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    Closing Pool - Blowing out main drain

    Hello everyone,

    I am closing my pool and have blown out and plugged all of the skimmer and return lines. However I am very confused about my system when attempting to blow out my main drain.

    There are two pipes going into the pump. One of them has a jandy valve, I assumed this is the main drain pipe. However when the valve is open and I am pumping air into the system air does not escape from the main drain. In fact the pressure builds and eventually one of the return lines give in and plug blows. When I close the valve however the main drain does get blown out. Which is very puzzling to me. How would I seal the main drain?

    Please let me know if you need me to provide any more info.

    Thanks in advance
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    Re: Closing Pool - Blowing out main drain

    Q: How many Jandy Valves do you have and what does it operate?

    If I am understanding you correctly, you were able to remove the water from the return jets and skimmers, then successfully plugged them. When you worked on the main drain, the plug from one of the returns blew out. Then you closed the valve to the return or skimmer (not sure), and you were successful in removing water form the main drain?

    Q: Do you only have one Jandy valve that operates the skimmer(s) and/or main drain?

    If this is the case, chances are that only the main drain or skimmer can operate at the same time, or you could have both open, but not both closed. If this is true, then after removing water from the main drain, close the valve and create the "air lock" in the main drain. Air is trapped in the line until the end of the run, near the bottom of the pool. It is highly recommended that you add a black plug in the pump housing as a secondary measure, both on the suction and return side.

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    One more note. If air is building up and the plug is blown out, that means your main drain is closed, otherwise the air would travel towards that area. You may not have enough volume to create a bubbling effect, but if the returns and skimmers are closed properly, both the main drain and returns/skimmer plumbing airway is open, then this should not be happening.
    14,700 gallons IG Pool Vinyl Liner - Octal Circulation System
    Hayward Pro-Series 350 LB. Sand Filter Model # S270T - 2" Plumping
    Hayward CL2002 Chlorinator - Hayward Super Pump 2 HP Model # k48m2n111
    Hayward AQR9 SWG 25K Salt Cell & TF-100 Test Kit + Speed Stir
    Gulfstream HE125RA - 117K BTU Heat Pump - Date of Build is 11-2013

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    Re: Closing Pool - Blowing out main drain

    Q: How many Jandy Valves do you have and what does it operate?
    There is 1 valve on the suction side, which is shown in the pic. and there is another one on the pressure side after the filter. I reckon it might be for the booster pump, but I am not sure. The pressure side valve is before the heater, but it does not by pass the heater.

    If I am understanding you correctly, you were able to remove the water from the return jets and skimmers, then successfully plugged them. When you worked on the main drain, the plug from one of the returns blew out. Then you closed the valve to the return or skimmer (not sure), and you were successful in removing water form the main drain?


    Yes you are correct. I was successful in removing water from main drain, but I am not sure if the water filled back in after I turned the air compressor off. I was able to remove the water from the main drain when the jandy valve was in the closed position. When it is in the open position the main drain does not bubble.


    Q: Do you only have one Jandy valve that operates the skimmer(s) and/or main drain?
    Yes there is only 1 valve.


    If this is the case, chances are that only the main drain or skimmer can operate at the same time, or you could have both open, but not both closed. If this is true, then after removing water from the main drain, close the valve and create the "air lock" in the main drain. Air is trapped in the line until the end of the run, near the bottom of the pool. It is highly recommended that you add a black plug in the pump housing as a secondary measure, both on the suction and return side.


    This is what is confusing to me. The main drain only drains when the valve is in closed position.

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    Re: Closing Pool - Blowing out main drain

    I was successful in removing water from main drain, but I am not sure if the water filled back in after I turned the air compressor off. I was able to remove the water from the main drain when the jandy valve was in the closed position. When it is in the open position the main drain does not bubble.
    If you have one valve that operates the skimmer and main drain, maybe you have this reversed. I am assuming that you can have both the MD and skimmer open at the same time. Then you can either close the MD, but not the skimmer, and vice versa. Once the MD blows, then close the valve and create an "air lock".

    I am guessing that if the Jandy valve was in the closed position, this would be for the skimmer. After blowing out lines in main drain, then turn the valve until you hear pressure build up with pump running, meaning you created the "air lock", then quickly shut off pump. I suggest you plug the pump return side with black plugs, as this will redirect air flowing towards the main drain. If the skimmers are closed, you will not have an issue with the plugs popping out.
    14,700 gallons IG Pool Vinyl Liner - Octal Circulation System
    Hayward Pro-Series 350 LB. Sand Filter Model # S270T - 2" Plumping
    Hayward CL2002 Chlorinator - Hayward Super Pump 2 HP Model # k48m2n111
    Hayward AQR9 SWG 25K Salt Cell & TF-100 Test Kit + Speed Stir
    Gulfstream HE125RA - 117K BTU Heat Pump - Date of Build is 11-2013

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    Re: Closing Pool - Blowing out main drain

    Thanks for the help I think I figured out my issue.

    The valve is actually in the off position when handle is parallel with with pvc pile and in on position when it is perpendicular. Which sounds very unusual to me.

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    Re: Closing Pool - Blowing out main drain

    Did you close the main drain and create the "air lock"? It sounds like it is in reverse of what you thought, correct? At least you resolved your issue.
    14,700 gallons IG Pool Vinyl Liner - Octal Circulation System
    Hayward Pro-Series 350 LB. Sand Filter Model # S270T - 2" Plumping
    Hayward CL2002 Chlorinator - Hayward Super Pump 2 HP Model # k48m2n111
    Hayward AQR9 SWG 25K Salt Cell & TF-100 Test Kit + Speed Stir
    Gulfstream HE125RA - 117K BTU Heat Pump - Date of Build is 11-2013

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    Re: Closing Pool - Blowing out main drain

    Will a two way ball valve keep the air in the main drain trough the winter after blowing out the water?
    19K gal AG. 200 Swimpro Element Filter. 2HP, Dual Speed Voyager. TF-100.

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    Re: Closing Pool - Blowing out main drain

    Quote Originally Posted by puchasr View Post
    Will a two way ball valve keep the air in the main drain trough the winter after blowing out the water?
    If the valve is closed and an "air lock" has been created, then the answer is YES. Please plug the suction and return side with black rubber plugs inside the pump basket as extra insurance.
    14,700 gallons IG Pool Vinyl Liner - Octal Circulation System
    Hayward Pro-Series 350 LB. Sand Filter Model # S270T - 2" Plumping
    Hayward CL2002 Chlorinator - Hayward Super Pump 2 HP Model # k48m2n111
    Hayward AQR9 SWG 25K Salt Cell & TF-100 Test Kit + Speed Stir
    Gulfstream HE125RA - 117K BTU Heat Pump - Date of Build is 11-2013

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