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Thread: chlorinating/filtering only once/twice a week

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    Diver's Avatar
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    chlorinating/filtering only once/twice a week

    [not sure where this topic should go, move it if needed]

    I introduced my fried to TFP last year and he’s been enjoying the results since. His pool was on a colder side so I also recommended a solar cover. He got the cover this year. His pool is a weekend only pool, meaning nobody uses it during the week days.

    He developed an interesting approach to maintaining his pool. He chlorinates it at the end of the weekend to above normal range level, covers it with solar cover and leaves it as is until Friday night. He doesn’t even run the pump. The cover covers almost 100% of the pool so the loss of chlorine is minimal.

    He checks the levels before weekend, chlorinates if needed, runs the pump overnight and vacuums whatever ended up on the pool floor. And that’s it.

    Chlorine loss is a percentage of the concentration so higher levels lose more chlorine. Hover, my understanding it’s only pertains to loss from UV. Loss due to organics will be proportional to the actual usage. So he doesn’t experience excessive loss due to higher levels of FC.

    Does anyone do something like this? Any thoughts on viability of this method?
    26K In-ground Vinyl Pool | Hayward DE4820/SP0710XR50 filter | 1.125 HP Dual Speed Hayward Super Pump | Aquasol Solar

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    Mod Squad Bama Rambler's Avatar
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    Re: chlorinating/filtering only once/twice a week

    While it appears to be working somewhat in his case, it could soon bite him. That's ok as long as he is willing to accept the risk. I'm guessing that he has an opaque cover.
    Dave J. TFP Moderator
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    Re: chlorinating/filtering only once/twice a week

    I am not sure I like the idea of no circulation, particular right after chlorination, but this method can indeed work, depending on CYA level, and how high a dosage he uses. The solar blanket will cut back on CL loss to UV rays, so if there are no organics, it will work. Again, he should at the very least run the pump when adding chlorine. He may do so, but I am inferring from your post that he doesn't. Also, this will only work as long as his chlorine does NOT dip below an acceptable level. He doesn't check on it apparently, just leaves it covered for the week. He will probably get burned at some point!
    13'x22'x52" 8,000 gallon ProSeries Pool with Borates
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    Diver's Avatar
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    Re: chlorinating/filtering only once/twice a week

    he does run pump while chlorinating...
    26K In-ground Vinyl Pool | Hayward DE4820/SP0710XR50 filter | 1.125 HP Dual Speed Hayward Super Pump | Aquasol Solar

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    mas985's Avatar
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    Re: chlorinating/filtering only once/twice a week

    Going a week without any circulation, I would be a little concerned about dead spots where algae could bloom. Any reason he couldn't run the pump maybe 30 min/day just to mix up the water some?

    Also, if he has to raise the chlorine by a lot at the beginning of the week, it could degrade the cover faster. The bubble covers don't last long in high chlorine environments.
    Mark
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    Re: chlorinating/filtering only once/twice a week

    Even the losses of chlorine from oxidation are proportional to the chlorine concentration -- they are just much lower compared to losses from sunlight. Is the cover nearly opaque or does it let some sun shine through? The chlorine loss rate will also be a function of water temperature. In my pool with a mostly opaque cover and 88ºF water temp during the day (dropping to 84-85ºF at night), I lose around 15% of the FC per day so I dose only twice a week. It's around 0.6 ppm FC per day where about 0.2 ppm of that is chlorine oxidation of CYA and most of the rest is probably chlorine oxidation of the solar cover. My pump runs for 8 hours during the day.

    By his not running the pump, the chlorine oxidation of his cover will use up chlorine near the cover so that rate of loss will be cut down so his overall loss rate will drop (there is still some mixing from diffusion, but it is slow), but there is the possibility that algae could start to grow on the underside of his cover, possibly creeping in from the sides if the chlorine level is depleted near the cover. It might be interesting for him to carefully take a chlorine sample right from under the cover near the water's surface after a week has elapsed (i.e. before he next doses) and compare that with a sample taken a foot or two below the surface.

    As Mark indicates, having a little bit of pump runtime each day should help prevent dead spots from forming. On the flip side, is that it would likely increase the chlorine loss rate. It would be interesting to see, if he's willing to take measurements both ways.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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    Diver's Avatar
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    Re: chlorinating/filtering only once/twice a week

    thank you guys for your responses. I will let him know and post back if he has some interesting results
    26K In-ground Vinyl Pool | Hayward DE4820/SP0710XR50 filter | 1.125 HP Dual Speed Hayward Super Pump | Aquasol Solar

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    Re: chlorinating/filtering only once/twice a week

    He's doing things the right way, to a point. If he's not losing FC, he doesn't need to add anymore. I wouldn't go that long without circulation, myself. That's why they make timers. Besides having dead spots where algae can grow, I'll bet he also has tremendous temperature stratification. I hate that. You dip your toe in and think "Ooooh, nice!" and jump in only to shoot right back out like a submarine-launched Polaris missile when you hit the ice water a few feet down.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
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    Re: chlorinating/filtering only once/twice a week

    I have an opaque Aquamatic cover, so my pool loses very little FC. I only need to add bleach about once per week myself, but I always run my pump for 8-12 hours per day. I do not like the idea of stagnant water at all!
    32000 Gallon 18'X40' Rectangular Gunite pool. Pentair 60sqft DE filter. Electric heat pump. Aquamatic Pool Cover.

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    Re: chlorinating/filtering only once/twice a week

    bolleat, what's your water temp, FC start, CYA and FC drop over the week?
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    Re: chlorinating/filtering only once/twice a week

    Quote Originally Posted by Richard320
    I'll bet he also has tremendous temperature stratification. I hate that. You dip your toe in and think "Ooooh, nice!" and jump in only to shoot right back out like a submarine-launched Polaris missile when you hit the ice water a few feet down.
    That's another thing to consider, especially if he's trying to get his water warmer. My understanding is his solar cover will be more efficient if he gets a timer and does a little bit of circulation multiple times a day. If the water on the top couple inches is warmed to the 90's, it's now less efficient and much harder and slower for further warming from the sun/solar cover. Even just a 10 dollar timer set at 30 min run time 3 times a day during peak sun hours.
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