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Thread: couldn't blow the main line

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    botanica37's Avatar
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    couldn't blow the main line

    I tried blowing it from the pump basket, with the pool intake valve open, but nothing would come out of the main drain. Is there another way to blow the main line?

    Thanks!
    free form 40k gal, IG, plaster, Triton II 100C sand filter, Lite 2 heater
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    Mod Squad JohnT's Avatar
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    Re: couldn't blow the main line

    It takes a lot of pressure. A shop vac usually won't do it. You are lifting a bunch of water.
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    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

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    Re: couldn't blow the main line

    What I would do is place a string across the MD and see if it moves.

    As long as you can evacuate enough water to be below the frostline, you should be OK
    Luv& Luk
    -Ted

    Having done construction and service for 4 pool companies in 4 states starting in 1988, what I know about pools could fill a couple of books - what I don't know could fill a couple of libraries :-D

    POOL SCHOOL, TF Testkits, Jason's Pool Calculator, CYA vs. cl chart, (Just a few DARNED handy links!)

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    botanica37's Avatar
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    Re: couldn't blow the main line

    I was using a compressor and nothing moved at all. It is almost like that the air was going somewhere else? Since I was trying to blow it from the pump basket, I am assuming that the only thing that could stop the air will be the direction valve which is on the intake line and separates the spa and the pool. I had the spa closed, so that would mean that the line to the main drain should be open. Does that sound right? I could see tiny bubbles coming out of the skimmer, even though it was already plugged...I was afraid that too much PSI will crack the line...

    I just did a search on VA frost line and it seems to be 16-18 inches. I think my main line is way below that, so I am safe?
    free form 40k gal, IG, plaster, Triton II 100C sand filter, Lite 2 heater
    1 1/2 HP Pentair Ultra Flow High Performance pump
    Caretaker in-floor cleaning system

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    Re: couldn't blow the main line

    Quote Originally Posted by botanica37
    I was using a compressor and nothing moved at all. It is almost like that the air was going somewhere else? Since I was trying to blow it from the pump basket, I am assuming that the only thing that could stop the air will be the direction valve which is on the intake line and separates the spa and the pool. I had the spa closed, so that would mean that the line to the main drain should be open. Does that sound right? I could see tiny bubbles coming out of the skimmer, even though it was already plugged...I was afraid that too much PSI will crack the line...

    I just did a search on VA frost line and it seems to be 16-18 inches. I think my main line is way below that, so I am safe?
    Well, you have to be sure you are not losing air out the output/filter/return side of the pump. When blowing suction side, I set MPV to closed and shut down all return lines. Otherwise air WILL leave first through the return side as they exit into shallower water than the MD.

    When you say pump basket--did you mean the intake hole or are you blowing into the drain plug? If the former, what I said does not apply, but I would think it is hard to get a good seal that way.
    Current: 28,000G 18'x36' I/G AnthonySylvan Plaster; Waterway 60 sq.ft. DE Filter; 1.0hp x 1.65 SF Two-Speed (B2982) WhisperFlo; 2004-Present
    Previous: 40,000G 20'x40' I/G Koven unlined WWII salvage 5/8" marine steel; Lomart Stainless Sand Filter; 3/4hp Hayward SuperPump; 1946-2003 (managed by me from about 1964)
    Ancient Taylor K-2000, upgraded with Taylor CH, TA, and FAS-DPD, and TFT CYA tests.

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    botanica37's Avatar
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    Re: couldn't blow the main line

    I tried the intake hole with expansion plug. If you think I will get better results with the drain hole, I will try to find a fitting for it.
    free form 40k gal, IG, plaster, Triton II 100C sand filter, Lite 2 heater
    1 1/2 HP Pentair Ultra Flow High Performance pump
    Caretaker in-floor cleaning system

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    Re: couldn't blow the main line

    If you are getting a good seal, then it won't make any difference to blow into the drain. If you are not getting a good seal, then it will. You should be able to tell. Waste is right, tie a string to your telepole and lay it over the drain. If you at least have flow out the drain you are probably below the frost line and all is good. If there isn't any, then you may be losing the air elsewhere and you are not accomplishing anything.
    Current: 28,000G 18'x36' I/G AnthonySylvan Plaster; Waterway 60 sq.ft. DE Filter; 1.0hp x 1.65 SF Two-Speed (B2982) WhisperFlo; 2004-Present
    Previous: 40,000G 20'x40' I/G Koven unlined WWII salvage 5/8" marine steel; Lomart Stainless Sand Filter; 3/4hp Hayward SuperPump; 1946-2003 (managed by me from about 1964)
    Ancient Taylor K-2000, upgraded with Taylor CH, TA, and FAS-DPD, and TFT CYA tests.

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    Re: couldn't blow the main line

    If you slowly pour RV antifreeze into the MD line from the pump suction side, it will displace pool water back into the pool. If you pour enough in you will be able to see it coming out of the MD, but you only need to add enough to fill the line down to below the freeze/frost line on the pump end.
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    Re: couldn't blow the main line

    This year I blew my lines from my cart filter drain plug.

    A shop vac put about 3 psig on the gage when blowing the returns and skimmers. I used a compressor with a trigger blower and a return plug with the metal pieces taken out. It showed about 7-8 psig while blowing the main drain.

    If you aren't building any pressure, and using a compressor, the air is going somewhere else.
    30,000 gallon vinyl / Starite pump, Sys 2 cartridge, Max-E-Therm 333k heater / Bioguard SWG

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    botanica37's Avatar
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    Re: couldn't blow the main line - an update

    After a lot of thinking and being concerned that I couldn't blow the main line I called the pool guys to blow the lines. They used Mighty Vac and rechecked all my lines and a LOT of water came out, even though I thought that I had blown all the water with the compressor. So, I am guessing that the compressor doesn't cut it (high pressure, low volume), I did it wrong? or it is normal to have some water left in the pipes ?

    If possible, I would be interested in finding out what is the output of the Mighty vac and if any of the Ridgit/Shop Vac comes closer for a lower price? I couldn't even find any info on Mighty vac online.

    Thanks!
    free form 40k gal, IG, plaster, Triton II 100C sand filter, Lite 2 heater
    1 1/2 HP Pentair Ultra Flow High Performance pump
    Caretaker in-floor cleaning system

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    Re: couldn't blow the main line

    The vac/ blowers that the 'pros' use are ~ 3 - 4 hp and meant to utilize the full HP for either suction or blowing.

    When we plumb a new pool, the majority of the lines run well below the frostline, so if there is a little water left in them once we blow them out, it's simply not an issue

    Please remember that we do a quick 'in and out' closing and that a pool owner with the proper equipment can do a MUCH better job, over the course of a couple days, than what we do in 1 &1/2 hours
    Luv& Luk
    -Ted

    Having done construction and service for 4 pool companies in 4 states starting in 1988, what I know about pools could fill a couple of books - what I don't know could fill a couple of libraries :-D

    POOL SCHOOL, TF Testkits, Jason's Pool Calculator, CYA vs. cl chart, (Just a few DARNED handy links!)

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