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Thread: Draining a pool connected to sewer system

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    Draining a pool connected to sewer system

    I'm planning on draining my pool due to high CYA levels and had a few questions.

    First, the waste output from my filter goes directly into the ground (and I assume is connected to the sewer system).

    When I backwash the system, the pressure on the filter fluctuates wildly (0-20 continuously on the dial) and there are a lot of cavitation sounds. I'm wondering if the pump is trying to push water into the sewer system at too high of a rate or if that is simply normal.

    While I could rent/buy a pump and hook it directly to the cleanout line, that seems like an expensive alternative if I can simply use the waste line to drain the pool.

    I'd also like suggestions on draining it all in one shot (I need to drain at least 75% of water) versus doing partial drains/refills.
    ~10K Gallon IG Plaster Pool built in 1996
    AO Smith SQ1152 1.5HP Pump
    Sta-Rite T-240BP-1 Sand Filter (62 GPM)

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    mas985's Avatar
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    Re: Draining a pool connected to sewer system

    The problem is likely that there is too little head loss in the backwash side of the plumbing so the pump may be cavitating although you might just be hearing high velocity water noise which is not a problem. Cavitation sounds like small pebbles going through the pump.

    But you should be able to get to 75% drain with just the pool pump as long as you can isolate the main drain to the pump.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Draining a pool connected to sewer system

    I decided to just go and test draining it as designed and it worked great. No pressure fluctuations and was draining nice and smoothly.

    I've ordered a float valve for the skimmer and will see about doing a full drain once it arrives.
    ~10K Gallon IG Plaster Pool built in 1996
    AO Smith SQ1152 1.5HP Pump
    Sta-Rite T-240BP-1 Sand Filter (62 GPM)

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    mas985's Avatar
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    Re: Draining a pool connected to sewer system

    Just a word of caution on the float valve. They have a tendency to leak when the suction gets high. So you need to make sure the seal is very clean (i.e. no debris entering the skimmer) and you have a bit of pool lube on the o-ring. Otherwise, the pump will lose prime and if the pool level is too low it is nearly impossible to get it to prime again.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Draining a pool connected to sewer system

    My diverter valve is arriving today and I had a question.

    There is an O-ring already installed at the bottom of the skimmer, but no idea how old it is. Should I replace with the one that comes with the diverter or simply put pool lube on the current one?
    ~10K Gallon IG Plaster Pool built in 1996
    AO Smith SQ1152 1.5HP Pump
    Sta-Rite T-240BP-1 Sand Filter (62 GPM)

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    Mod Squad jblizzle's Avatar
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    Re: Draining a pool connected to sewer system

    While the existing may be fine, I would just go ahead and use the new one.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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    Re: Draining a pool connected to sewer system

    Quote Originally Posted by mas985 View Post
    Just a word of caution on the float valve. They have a tendency to leak when the suction gets high. So you need to make sure the seal is very clean (i.e. no debris entering the skimmer) and you have a bit of pool lube on the o-ring. Otherwise, the pump will lose prime and if the pool level is too low it is nearly impossible to get it to prime again.
    I think I'm running into this exact problem. The O-Ring that came with my diverter valve was too thin, so I put some pool lube on the old one and put it back in.

    Once the water level dropped below the entrance to the skimmer, it started this cycle.

    Water level in skimmer bottom would slowly drop until it emptied completely whereupon it would fill again from the equalizer pipe from main drain. This would pop up the float and break the seal. The pump would regain prime and the float would descend again and then the cycle would repeat itself. I even tried holding down the float manually to ensure a tight seal, but to no avail.

    Another odd thing was that, during this cycle, I was seeing water coming up in two places in the yard (not a lot, just bubbling). This happened when the pump starting losing prime and air was getting in.

    I'm think that I bought the right diverter, but not sure. It is a Pentair Skimmer and I ordered this (http://www.amazon.com/gp/product/B004VU8TL2). It settles down nicely into the prongs at the bottom of the skimmer basket.

    For now, I'm going to do partial drains/refills, but it would be nice to be able to do it the proper way.

    Suggestions welcome!
    ~10K Gallon IG Plaster Pool built in 1996
    AO Smith SQ1152 1.5HP Pump
    Sta-Rite T-240BP-1 Sand Filter (62 GPM)

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    Mod Squad jblizzle's Avatar
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    Re: Draining a pool connected to sewer system

    The o-ring is what the entire valve sits on, but the float in the middle just drops down and is a plastic on plastic interface ... I think that is where it often leaks when trying to attempt this and is not really designed to be air tight.

    If you are trying to force the suction to only be from the floor, might work better with just a solid round plate that you can set on the o-ring in the bottom of the skimmer.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
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    Re: Draining a pool connected to sewer system

    After raiding the kitchen, I found a lid to a cookie tin that worked perfectly. I had to babysit it a bit as it would periodically lose water in the skimmer, but much better than before.

    Actually, it worked a bit too well. It was pumping too fast for the waste line to handle and started filling up my back yard and into my neighbors so I had to call a halt after I had drained about a foot or so. Since I have a single-speed pump, not sure what else I can try.

    Am actually wondering if the waste pipe is simply diverted into the back yard and isn't actually connected to the sewer system.

    Another puzzling thing is why I only get the overflow into the back yard when I'm draining from the main drain and not from the Skimmer.
    ~10K Gallon IG Plaster Pool built in 1996
    AO Smith SQ1152 1.5HP Pump
    Sta-Rite T-240BP-1 Sand Filter (62 GPM)

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    Mod Squad jblizzle's Avatar
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    Re: Draining a pool connected to sewer system

    My waste pipe goes underground for about 10 feet and just ends in a hole. So certainly possible it is not connected to anything ... or maybe it cracked.

    I am guessing when you are draining from the skimmer, you are not draining as much volume and maybe the groud can handle it.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
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    mas985's Avatar
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    Re: Draining a pool connected to sewer system

    Since I have a single-speed pump, not sure what else I can try.
    Sump Pump?

    http://www.homedepot.com/p/Wayne-3-4...specifications

    Is the pool surface much higher than the drain point? A siphon is an option but you would have to drain and fill at the same time and at different locations (e.g. deep end, opposite end surface). I have done this with my pool but using the main pump on low speed (instead of a siphon) and it works pretty well for a partial refill. Solves the skimmer seal problem. But it would take a long time with just a siphon unless the pool is a lot higher than the drain point.

    Sump pump is probably your best option.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    CUTiger78's Avatar
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    Re: Draining a pool connected to sewer system

    Here's one thing you can try to avoid having the skimmer run dry - put the hose end of the manual vac into the skimmer hole and put the vac head in the deep end. I get a good enough seal that way to run the pump at water levels way below skimmer level.

    Might exacerbate your water in the backyard problem, though.

    Good luck!




    36K gallon 42X22 gunite/plaster kidney-shaped IG;
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    jrs_diesel's Avatar
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    Re: Draining a pool connected to sewer system

    When I did my partial drain and fill, I ran into the same problem. My main drain line goes to the skimmer too which has the float valve. I used my vacuum hose attached to the pressure side cleaner line (for the Polaris) and ran the other end to the sewer cleanout on the house.

    Once the level dropped below the level of the skimmer and started sucking air, the float valve shut and the pump pulled from the main drain only. The float valve does not have a perfect seal, as noted above. All i did was keep water in the skimmer above the float valve. The suction of the pump kept the float shut, while the water kept air away from the valve. I had to add a small bucket every 20 - 30 minutes to keep enough water in the skimmer.
    J.R.

    20K IG gunnite pool
    2HP Hayward single speed pump
    Cartridge filter

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    Re: Draining a pool connected to sewer system

    I went to Harbor Freight to pick up a 1/6 HP pump that I'd seen recommended here (http://www.harborfreight.com/16-hors...8422-8394.html), and came home with something completely different. For the same price, I bought a 1HP 'Dirty Water' pump with more than double the pumping speed (http://www.harborfreight.com/1-horse...oat-69300.html).

    The only drawback is that it will only drain down to 3" instead of .5", but that isn't an issue since I don't need to drain the entire pool. I'm certainly enjoying the faster speed. It has been going for 3 hours and the water level is already down over 50%.

    Will post new chemistry numbers in a few days once it is refilled!
    ~10K Gallon IG Plaster Pool built in 1996
    AO Smith SQ1152 1.5HP Pump
    Sta-Rite T-240BP-1 Sand Filter (62 GPM)

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