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Thread: Specific reason not to add bleach to skimmer?

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    Specific reason not to add bleach to skimmer?

    Hi All,

    My pool builder, who generally (but not always) gets things right, says to add bleach to the skimmer, not directly to the pool, because on the one hand I have a vinyl liner (potentially bleached by the bleach), and on the other hand a sand filter, which is unaffected by the bleach (supposedly). I'm posting this question here because I understand the TFP recommendation is to add to the pool in front of the jets and then brush, but I asked a follow-up question about what specific components in my filter/pump system might be damaged by the direct addition of bleach, and didn't receive an answer.

    This isn't a big deal obviously, but I prefer to add to the skimmer, so long as I'm not damaging anything (gaskets, maybe?). So, back to my question: what specifically is the potential damage from adding bleach to the skimmer?
    IG, vinyl (27 mil), 12,000 G, Apr 2016, OREQ TK400 test kit
    Pentair Tagelus sand filter, Intelliflow variable speed pump, automatic cl/br feeder
    solar bubble pool cover, full sun ~8 hrs/d, water temp 79-84 F May-Oct
    municipal water supply has low nitrates (<0.4 ppm), sulfates, turbidity, TDS
    don't know about phosphates, but suspect they are low (no agriculture around)

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    JoyfulNoise's Avatar
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    Re: Specific reason not to add bleach to skimmer?

    Bleach isn't as big a deal as acid. Acid in the skimmer is a no-no because it can lead to advanced degradation of heater cores and pump seals as well as cause a mess in the filter by turning organic compounds (like oils) into thickened mess.

    However, if you go to the deep end of your pool and add bleach by slowly pouring (thin pencil diameter stream) into the water stream of one of the returns with the pump running on high speed (assuming there's a 2-speed or variable speed pump), then the bleach will be so diluted it will never hit the bottom of your pool. If you pour bleach or acid directly in the water with no mixing, then yes it will pool on your liner. But, if you follow TFP recommended procedure and follow up with a quick brushing of the pool walls (which you should do at least once a week anyway), then you will never have to worry about a bleached liner. Bleached liners happen when people get lazy and distracted and don't follow proper chemical handling procedures.
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Re: Specific reason not to add bleach to skimmer?

    Thanks Matt, this is helpful. I do add acid directly to the pool for the general reason you mention, although I hadn't known about the specific problem of messifying (scientific term) the OCs in the filter. So definitely will continue to add acid directly to the pool (which is a rare event in any case).

    In the case of bleach, it seems like the potential problem is degradation of rubber seals in the pump. (I don't have a heater.) Any studies or theory on this? If typically the pump fails for reasons other than accelerated oxidation of seals by chlorine, then, well, no harm in adding bleach to skimmer. But it isn't too much harder to pour into pool and brush, which I do all the time anyway (subject only to my concern that brushing does in principle abrade my liner). Maybe I'll flip a coin on this one...
    IG, vinyl (27 mil), 12,000 G, Apr 2016, OREQ TK400 test kit
    Pentair Tagelus sand filter, Intelliflow variable speed pump, automatic cl/br feeder
    solar bubble pool cover, full sun ~8 hrs/d, water temp 79-84 F May-Oct
    municipal water supply has low nitrates (<0.4 ppm), sulfates, turbidity, TDS
    don't know about phosphates, but suspect they are low (no agriculture around)

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    JoyfulNoise's Avatar
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    Re: Specific reason not to add bleach to skimmer?

    The biggest concern inside the pump is really the shaft seal not so much the rubber o-rings. A large bleach load into the pump is going to have both high chlorine content (hypochlorite) as well as high pH (from the excess lye in bleach). That is certainly not great in terms of materials but the plastic and rubber materials will withstand the momentary surge. The shaft seal is the most likely component to be degraded by the chemical stress. The shaft seal is the one component inside the pump that seals the water from the motor shaft that is turning the impeller. Once the shaft seal is compromised, water will leak into the motor and the bearings will begin to corrode and eventually seize. Acid, of course, is far worse than bleach in this regard. I have no specific data on likelihood of occurrence or increased risk, it's just something we say not to do since it is what you might call an "avoidable risk".

    That said, the handling of bleach is really the biggest concern. Most people just find it easier to pour bleach directly from its container into the pool near a return. In my pool layout, the skimmer would be the least optimal place to pour chemicals into because it requires aiming the pour into a smaller hole with the potential to splash out onto my nice flagstone coping. Bleach does stain concrete and decking materials if the concentrated liquid hits the surface. Your clothes will also eventually get bleach spots on them. So minimizing the effects of pouring & splashing is really where the benefit of putting it straight into the pool comes into play.

    I rarely have to add bleach to my pool because I have an SWG pool. When I do (in the winter months), I always pour it into the deep end and then brush. It is just the optimal process for me.
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Re: Specific reason not to add bleach to skimmer?

    OK, thanks, that's helpful, and persuasive. I'm not terribly concerned about splash out, since I pour the bleach first carefully into a measuring cup. But the downside risk of degrading the shaft seal is greater than having to brush, so I'll be pouring it into the pool henceforth.

    I've also been considering a SWG, and within the next few weeks might re-examine the threads on that here.
    IG, vinyl (27 mil), 12,000 G, Apr 2016, OREQ TK400 test kit
    Pentair Tagelus sand filter, Intelliflow variable speed pump, automatic cl/br feeder
    solar bubble pool cover, full sun ~8 hrs/d, water temp 79-84 F May-Oct
    municipal water supply has low nitrates (<0.4 ppm), sulfates, turbidity, TDS
    don't know about phosphates, but suspect they are low (no agriculture around)

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    JoyfulNoise's Avatar
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    Re: Specific reason not to add bleach to skimmer?

    This is a good place to start -

    Economics of Saltwater Chlorine Generators

    And if you want to look up a comparison chart of all the commercially available units -

    Discount Salt Pool - Compare Chlorine Generators and Chlorinators
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Re: Specific reason not to add bleach to skimmer?

    Thanks Matt, that's really good info. on SWGs. Since I have an automatic chlorine dispenser that works well for now, and I have a lot of bleach for back-up and spiking, I'll probably just run down my tri-chlor supply, with the feeder on pretty low, until I get to the proper CYA level, and then see how much of a pain it is to add bleach regularly. I've looked at the other chlorinating options discussed on this site, and it seems that, in the absence of low-CYA tabs for my feeder, the long-run options are bleach or a SWG. I'll see.
    IG, vinyl (27 mil), 12,000 G, Apr 2016, OREQ TK400 test kit
    Pentair Tagelus sand filter, Intelliflow variable speed pump, automatic cl/br feeder
    solar bubble pool cover, full sun ~8 hrs/d, water temp 79-84 F May-Oct
    municipal water supply has low nitrates (<0.4 ppm), sulfates, turbidity, TDS
    don't know about phosphates, but suspect they are low (no agriculture around)

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    Mod Squad tim5055's Avatar
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    Re: Specific reason not to add bleach to skimmer?

    Quote Originally Posted by szmad View Post
    in the absence of low-CYA tabs for my feeder, the long-run options are bleach or a SWG. I'll see.
    If/until someone changes the laws of physics, don't expect a low-CYA tab. In its natural state chlorine is a gas, so to make it useable (and sale able at the pool store) it needs to be bound to something. Those somethings are:

    CYA
    Calcium
    Lithium
    Water

    So far, the only thing the industry has come up with that works in erosion feeders like you have is tricolor tabs.

    There may be research out there as to other products, who knows.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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