Need advice on how much water to remove for salt ppm

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C

conmore

0
Jan 5, 2008
68
Geelong Australia
Hi there
I’m considering purchasing a new SWG. My old one happily operated at 5000ppm but it’s nearly 15 years old. The replacement SWG manual specifies a salt level of between 3000-3500ppm and no higher than 4000ppm.
Using an Aqua Chek salt test strip it returned a 7.2 result (4780ppm). So if I proceed with the SWG replacement I need to lower the salt level by diluting it with fresh water.
It’s a fibreglass inground pool with a volume of 30,000 litres (7900 gallons more or less) and is at max. level.
I’ve read a couple of formulas on websites but I don’t want to dilute it too much and have to add salt again hence my question. Any advice with an amount to remove would be very helpful.
Cheers
 
Depending on the salinity of your fill water, it is a straight correlation. If you need to reduce the salinity by 30%, drain 30% and refill.
 
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0.7 times 4780. 3350.

I bet your fill water has 100 ppm or so.

Do you have shallow water table?
 
mknauss said:
0.7 times 4780. 3350.

I bet your fill water has 100 ppm or so.

Do you have shallow water table?
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Our town water comes from a holding basin and is treated prior to the domestic supply. You may be right about the salinity but I’ve always assumed it’s next to zero. Right or wrong.
Can you explain the 0.7 (how did you come up with that figure) x 4780 and how that equates to nearly a third of the water having to be drained and refilled. Just wanting to understand it a bit better
Cheers
 
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If you remove 30% of your pool volume of 4780 ppm salinity water, and add back that amount of 0 ppm salinity water, you will result is about 3350 ppm salinity in the entire pool volume.
 
mknauss said:
If you remove 30% of your pool volume of 4780 ppm salinity water, and add back that amount of 0 ppm salinity water, you will result is about 3350 ppm salinity in the entire pool volume.
Click to expand...
I understand that. What I was asking was how did you arrive at the figure of 30% of the pool volume removed? Mathematically I guess. I figured out how you arrived at 0.7 but I’m not understanding the calculation of 30%. I don’t doubt it I just want to understand the working
Cheers.
 
Is there a reason why you set your eyes on that specific SWG? Easiest option would be to just get a SWG that is happy with your current salt level like the one you are replacing.

Many (if not most) Aussie SWGs are designed to run in the 4000-5000 ppm range.

I just replaced my old Hurlcon with an Astralpool SWG, was a direct replacement, both are specified between 3000-8000 ppm, happiest at 4000-5000 ppm.
 
The math works like this...
Your current salinity is 4780 ppm and your target salinity is 3000-3500 ppm. Pick a number in that target range (Marty chose 3350) and divide that by your current salt level.. 3350/4780 = 0.7008xxx or approximately 70%. That means that to keep only 70% of your salt (the 3350 target) you need to remove 30% of your water and replace it with fresh water. If your fill water has some salt...say 100 ppm...then you will end up slightly above that 3350 target but still under the 3500 maximum.
 
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Steve-D said:
The math works like this...
Your current salinity is 4780 ppm and your target salinity is 3000-3500 ppm. Pick a number in that target range (Marty chose 3350) and divide that by your current salt level.. 3350/4780 = 0.7008xxx or approximately 70%. That means that to keep only 70% of your salt (the 3350 target) you need to remove 30% of your water and replace it with fresh water. If your fill water has some salt...say 100 ppm...then you will end up slightly above that 3350 target but still under the 3500 maximum.
Click to expand...
Thank you vm. I was really keen to understand the formula to end up with the 30%. Now I understand.
 
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Also to answer the comment about purchasing an SWG that is more in keeping with the current salt level I’ve been working with since inheriting the pool some 14 years ago.
The issue I have is the SWG is no longer manufactured and getting either a replacement cell or getting it refurbished is a nightmare. The company that rebuilt my current cell 6 years ago is no longer so I’ve been researching SWG’s that are manufactured here in Australia and at this stage settled on a Crystal Clear RP3000 but I haven’t decided finally yet. It’s this SWG that stipulates the recommended ppm I asked about in my OP. But I’m open to suggestions. I think I prefer analogue over digital but I would do my research. I was looking at the earlier Hurlcon VX7T.
Cheers
 
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There are certainly other Aussie made chlorinators around, like Astralpool (used to be Hurlcon, but got bought by US company Fluidra and rebranded as Astralpool Australia - but still developing and manufacturing in Melbourne). Or Saltmate or Poolrite, if you prefer an analog one.

But I don't want to throw you back in your research. If a partial drain is not in issue for you, then ignore my comment. Just wanted to point out that there are no-drain options
 
mgtfp said:
There are certainly other Aussie made chlorinators around, like Astralpool (used to be Hurlcon, but got bought by US company Fluidra and rebranded as Astralpool Australia - but still developing and manufacturing in Melbourne). Or Saltmate or Poolrite, if you prefer an analog one.

But I don't want to throw you back in your research. If a partial drain is not in issue for you, then ignore my comment. Just wanted to point out that there are no-drain options
Click to expand...
Hi there
Definitely not sold on the drain option tbh. Has anyone reading these posts had any experience with Saltmate for example?
Cheers.
 
What is the reason why you prefer analog SWGs? Never used one. Can only say that I was very happy with the Hurlcon that came with the house, and I'm even happier with the Astralpool I replaced it with this year.
 
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