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Thread: Lowering Calcium Hardness

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    benavidescj's Avatar
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    Lowering Calcium Hardness

    I have a high CH (520 ppm) and would like to lower using the technique of removing water from the deep end drain and adding water to the shallow end. This would require the I shut off water to the returns and pool cleaner since I do not want water mixing during the process. My waste line is located between the filter and the three way valve. If I shut of water to the returns and pool cleaner I am worried about the back pressure on the pump and filter over the three or four days this process may take. Is it ok to have this kind of back pressure on the pump and filter for three or four days?
    Carlos
    Pool: 28,000 gallons IG; IC 40 SWG; Pentair 120 gpm cartridge filter; Marble finish; Pentair Wisperflow 1.5 hp; Polaris 360
    Spa: 350 gallon; Bromine
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    Re: Lowering Calcium Hardness

    If you run the pump for more than a few minutes, there will be water mixing more or less through out the pool, regardless of what skimmers/drains/returns you turn on/off.

    If replacing water is going to take several days, the best you can easily do is to replace water only when the pump is off and assume everything mixes when the pump is on. Depending on what percentage of your water you are trying to replace, that can still be fairly efficient. With CH at 520, you shouldn't need to replace all that much water. Replacing up to 50% of your water is still reasonable even with continuous mixing.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Richard320's Avatar
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    Re: Lowering Calcium Hardness

    I dream of having CH as low as yours some day....

    If you simply must drain & refill, here's an idea. They are selling these gigantic trash bags to haul out old Christmas trees. Must be 15' circumference at 10 or 12 feet long. They're probably still on sale in some stores. I bought one at Lowes when we got our tree, but it's opened up and flattened out beneath everything right now, so all we do is remove the lights, ornaments, and drape then pull the bag up and haul the thing out without shedding 50 lbs of dry needles. But I digress.

    Put the bag in the pool with the fresh water hose filling it. Try to match the pumpout speed to the refill speed. The water level will stay even but the two waters will not mix. When done, push the bag down into the pool all the way, grab a bottom corner and fish it out empty.
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    benavidescj's Avatar
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    Re: Lowering Calcium Hardness

    Quote Originally Posted by JasonLion
    If you run the pump for more than a few minutes, there will be water mixing more or less through out the pool, regardless of what skimmers/drains/returns you turn on/off.
    Jason,
    How can water be mixing if there is no water returning into the pool? As I stated there is only a small amout of water being drawn from the bottom drain. Assuming there is little wind and only a small amount of water being drawn from the bottom drain where is the mixing comming from? Also, I am more concerned with the back pressure on the pump. Is there an issue with back pressure on the pump?
    Carlos
    Pool: 28,000 gallons IG; IC 40 SWG; Pentair 120 gpm cartridge filter; Marble finish; Pentair Wisperflow 1.5 hp; Polaris 360
    Spa: 350 gallon; Bromine
    How to shock your pool

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    Re: Lowering Calcium Hardness

    Quote Originally Posted by benavidescj
    I have a high CH (520 ppm) and would like to lower using the technique of removing water from the deep end drain and adding water to the shallow end.
    Whats the advantage of this? Why not just drain partially and refill?
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Re: Lowering Calcium Hardness

    Quote Originally Posted by benavidescj
    Quote Originally Posted by JasonLion
    If you run the pump for more than a few minutes, there will be water mixing more or less through out the pool, regardless of what skimmers/drains/returns you turn on/off.
    Jason,
    How can water be mixing if there is no water returning into the pool? As I stated there is only a small amout of water being drawn from the bottom drain. Assuming there is little wind and only a small amount of water being drawn from the bottom drain where is the mixing comming from? Also, I am more concerned with the back pressure on the pump. Is there an issue with back pressure on the pump?
    You will empty the pool quickly that way. Your pump will remove water much more quickly than the hose will refill the pool. You can't starve the pump for water and run it for any length of time.

    Even with zero flow, calcium from the pool water will migrate into the replacement water. I'd use the bag idea.
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    benavidescj's Avatar
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    Re: Lowering Calcium Hardness

    Quote Originally Posted by bk406
    Quote Originally Posted by benavidescj
    I have a high CH (520 ppm) and would like to lower using the technique of removing water from the deep end drain and adding water to the shallow end.
    Whats the advantage of this? Why not just drain partially and refill?
    Partial drain and refill does have potential complications. I have a high water table. Also, exposing the finish has the potential of damaging it, I am told, although I have not seen evidence of this.

    I am just trying to lower my CH with as little impact on the pool as possible. I don't think that partial drain and refill is that big a deal, and as a matter of fact I have done it in the past, on this pool. I just thought I had seen the technique, of draining on the deep end and and filling on the shallow end, on this website before but am too lazy to go look for the thread.

    This pool cost me a ton of money and I tend to treat it like a baby. Or you can call me anal, engineers tend to be that way. Yea the CH is manageable and I have dealt with it for about a year now. My supply water CH is not that high and I thought that this Spring I would lower it a bit... cause I am anal.

    Even though I think it is a good idea, if I do the bag idea my wife will laugh at me for about a week. Then she will rat me out to my friends who will in turn laugh at me for another week... I think I will drain and refill. I get enough grief just by doing that, I can hear her now, "Why you draining the pool?". Just kidding, it's all good.
    Carlos
    Pool: 28,000 gallons IG; IC 40 SWG; Pentair 120 gpm cartridge filter; Marble finish; Pentair Wisperflow 1.5 hp; Polaris 360
    Spa: 350 gallon; Bromine
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    Re: Lowering Calcium Hardness

    Last year I used low speed on my two speed pump with a long hose to drain from the deep end while filling in the shallow end. I replaced about half of the water using this method and based upon the final salt, calcium and CYA levels, it doesn't look like there was much mixing of the old and new water. The fill and drain rates were about 7 GPM so after 24 hours, I had replaced about 1/2 the pool water. Here is the thread where I described what I did.

    Also, back pressure doesn't harm a pump, it is the build of heat which can create problems so as long as there is water flowing through the pump, there shouldn't be an issue. However, I would not attempt this with a single speed pump. It may be possible but you would need to put in a lot of extra return restriction to reduce the flow rate to match the fill rate so the pump would be operating close to dead head.

    If you only have a single speed pump, another option is to siphon water out of the deep end but the pool level needs to be higher than the siphon exit and it will probably take a lot longer.
    Mark
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    benavidescj's Avatar
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    Re: Lowering Calcium Hardness

    Quote Originally Posted by mas985
    Last year I used low speed on my two speed pump with a long hose to drain from the deep end while filling in the shallow end. I replaced about half of the water using this method and based upon the final salt, calcium and CYA levels, it doesn't look like there was much mixing of the old and new water. The fill and drain rates were about 7 GPM so after 24 hours, I had replaced about 1/2 the pool water. Here is the thread where I described what I did.

    Also, back pressure doesn't harm a pump, it is the build of heat which can create problems so as long as there is water flowing through the pump, there shouldn't be an issue. However, I would not attempt this with a single speed pump. It may be possible but you would need to put in a lot of extra return restriction to reduce the flow rate to match the fill rate so the pump would be operating close to dead head.

    If you only have a single speed pump, another option is to siphon water out of the deep end but the pool level needs to be higher than the siphon exit and it will probably take a lot longer.
    Great info! I guess I will abandon the effort since I do have a single speed pump and would be operating close to dead head as you describe. The amount of water that would be flowing through the pump, in my case, would only be equal to the amount of water that is being discharged throught the waste hose bib.
    Carlos
    Pool: 28,000 gallons IG; IC 40 SWG; Pentair 120 gpm cartridge filter; Marble finish; Pentair Wisperflow 1.5 hp; Polaris 360
    Spa: 350 gallon; Bromine
    How to shock your pool

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    Re: Lowering Calcium Hardness

    Have you considered using a small submersible pump instead? This topic has come up before and it seemed to be the best solution to me.
    20K gal IG plaster pool, Manually chlorinated with 6% bleach, 1.5 HP Sta-Rite Dura-Glas II pump, Pentair FNS Plus 48 DE filter, Polaris 280

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    benavidescj's Avatar
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    Re: Lowering Calcium Hardness

    Quote Originally Posted by Beez
    Have you considered using a small submersible pump instead? This topic has come up before and it seemed to be the best solution to me.
    Yes, I did think about it but cannot justify the expense, even though they probably do not cost very much. Well, maybe I will go look in Home Depot and check them out. I like tinkering. I know, I know, I need counseling... I can hear you guys talking in the corner .
    Carlos
    Pool: 28,000 gallons IG; IC 40 SWG; Pentair 120 gpm cartridge filter; Marble finish; Pentair Wisperflow 1.5 hp; Polaris 360
    Spa: 350 gallon; Bromine
    How to shock your pool

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    Re: Lowering Calcium Hardness

    Quote Originally Posted by benavidescj


    I like tinkering. I know, I know, I need counseling... I can hear you guys talking in the corner .
    Engineers. You guys just can't help it
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Re: Lowering Calcium Hardness

    Go to your local pool store and rent a submersible pump and drain off the water accordingly. Be sure to drain off enough the first time because you can always add more calcium.

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    benavidescj's Avatar
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    Re: Lowering Calcium Hardness

    Thanks for the idea!
    Carlos
    Pool: 28,000 gallons IG; IC 40 SWG; Pentair 120 gpm cartridge filter; Marble finish; Pentair Wisperflow 1.5 hp; Polaris 360
    Spa: 350 gallon; Bromine
    How to shock your pool

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