Fill water?

[andy]

I am going to be changing my pool from salt water to regular water. My fill water(well) has CH of 375. Is there a way to lower CH? Is there anything I can attach to my fill water before it enters the pool, like a water softener?

Is salt water heavier or lighter than regular water?

Also any suggestions on a good way to change out my water? I don't really want to totally drain my pool since I have a fiberglass pool and would have to brace it off quite a bit. Can I pump water out from the top(warm water) of the pool and place the fill hose(cold water) in the bottom of the pool. Warm water should stay higher than the cold water I would think? Kind of a crazy idea but any thoughts?

 

[duraleigh]

Yeah, I don't know for sure that anyone on the forum has actually done it but a water softener will reduce the calcium. Keep in mind a residential softener is not designed for that capacitry so it may take some time and a lot of changing out of the softener chemistry.

Is salt water heavier or lighter than regular water? Salt water is heavier

Probably the best method (again, I know of no one who's actually tried it) would be to take a plastic sheet and cover your entire pool with plenty of overlap. Start filling by running the new fill on top of the sheet and then withdraw the salt water underneath the pool at the same rate you fill. In theory, you should get pretty close to complete replacement.

Jason recommends (and he may have done this) a similar method that simply withdraws from the bottom deep end and refills simulataneously from the shallow surface. That is probably a more practical approach and will almost surely replace an adequate amount of your salt water.

 

[JasonLion]

It is problematic to lower CH levels. Typical water softeners can lower CH, but they replace the CH with salt, which you probably don't want, and they are not designed to work with anything near the volume of water used in a swimming pool. Other than that, there is one company in Arizona that can lower CH levels with a patented process, but they stick to their home area. I have also heard of a CH absorbing ball that can be put in the skimmer, but I have never heard from anyone who has actually tried one to see if it works nor can I find anyone who actually sells them.

 

[JasonLion]

Continuous dilution, adding water while draining water at the same time, is fine for dilutions up to 50%, and plausible for dilutions up to perhaps 75%, but as you dilute the water more and more the amount of water required starts to go up dramatically. To get a near complete water replacement would require huge amounts of water. If you want more than a 75% dilution the huge plastic sheet method is probably the best approach.

I doubt that you could keep the water from mixing in practice simply from the temperature and salt concentration difference. Such things do happen in the ocean sometimes, but that requires a complete lack of water turbulence and is problematic if the temperature and/or salt concentration differences are small. The water flow from adding and removing water would surely be enough to mix everything up.

 

[andy]

The plastic sheet idea sounds perfect! I might just try that one

 

[Guest]

Don't know why you are worrying about lowering the CH since the fill water is only 375 and that is not really that high. If you are going to be using an unstabilized chlorine source such as bleach or liquid chlorine (stay away from cal hypo) then the higher CH will actually work for you since you will want to run your TA on the very low side, perhaps even as low as 50 ppm to get best pH stability and minimize acid consumption. Since the pool is indoors trichlor would not be your best choice for chlorination. If you still want automation you might look into a peristaltic pump to dispense the liqud chlorine, possibly in conjucntion with an ORP controller to automate it since you already have part of the equipment you need. As far as pH regulation, this is most ofen done with either CO2 injections, which tends to raise TA requiring the use of acid to lower it back down or by using a peristaticl pump to dispense acid. Unstabilized chlorine will cause a slow pH rise in many cases similar to what is seen with.

You can do partial drains and refills using softened water even though the cacium and magnesium has been replaced with sodium because the total amount of sodium in the fill water will still be much less than the sodium content of your water as it stands now for use with the SWG. There will still be a dilution effect. If you get your salt level down to about 1000 ppm or less you should get a good handle on the corrosion problem but you might not eliminate it since indoor pools without stabilzier do suffer from more corrosion than outdoor, stabilized ones whehter they are salt pools or not.

 

[andy]

I finally had enough time to change out my water which went flawlessly. I used duraleigh's idea of laying a 30x50 sheet of plastic over the pool with a sump pump under it and a fill hose on top. It took about 21 hours to completely swap water(21,000 gal) out. The plastic trick works perfectly and I was able to change out virtually all of the water as the plastic sucks right down to the bottom of the pool while the fresh new water is on top.

My plan is to use liquid chlorine or bleach and try for now and leave my ph sensor and acid pump hooked up. Couple questions.

1. Which would be better for me to use, liquid chlorine or bleach?
2. With the new water, where should I start....How much of what chemicals should I add initially?
3. Any other suggestions?

Here are my current test results:
FC 0
CC 0
PH 7.3
TA 375
CH 400
CYA 0
PHOS 250ppb
SALT >200

Thanks! Andy

 

[JohnT]

1. Which would be better for me to use, liquid chlorine or bleach?

They are the same. If you can get the liquid chlorine from a pool store for a reasonable price, it is easier because you have fewer jugs to deal with. What you get at a pool store is 10 or 12% while bleach is 3.75(Dollar Store etc.) to 6%.

2. With the new water, where should I start....How much of what chemicals should I add initially?

Chlorine and CYA. I'd add enough bleach to get your chlorine to around 15ppm. That will be about three jugs of bleach per 10,000 gallons of pool water. Shoot for about 35ppm CYA. The easiest way to add the CYA is to put it in an old sock in the skimmer. Don't try to test for CYA until close to a week after you add it.

3. Any other suggestions?

You might want to add details about your pool and equipment to your signature, and your general location to your profile. Makes it easier for us to give specific advice.

 

[JasonLion]

For an indoor pool, CYA of 20-30 is enough, though it is difficult to measure levels as low as 20 reliably.

It would be good if you could bring down the TA level, though that can be a project. As long as the TA is that high you should keep the PH between 7.0 and 7.4. High TA levels will tend to push the PH up and if the PH goes up there could be calcium scaling. You probably don't have very much aeration, so the upward pressure on the PH will be low but it will happen. Fortunately the Total Control system's acid tank/pump will be able to keep the PH under control.

 

[andy]

I'll add the bleach today and also get some cya in there. Should I add muratic acid to try and lower the TA? I know this will also lower PH but it usually seems to raise up anyway.

 

[JasonLion]

To lower TA you add muriatic acid to lower PH to between 7.0 and 7.2 and then aerate the pool to bring the PH back up. Aeration can be provided by a fountain, waterfall, spa jets, air compressor, kids splashing, rain, etc. This process is then repeated as many times as needed to get the TA down to where you want it (it might take quite a few cycles). The acid lowers both the PH and TA, while aeration raises the PH and leaves TA where it was. When doing this you don't want PH getting too high while the TA is still high, which shouldn't be an issue given the TC system is monitoring the PH.

You could just set the Total Control system to hold the PH around 7.2 or 7.3 and let whatever natural aeration you have take care of the TA over time. Aeration will raise the PH but the TC system will add acid to maintain the PH, lowering the TA over time. The only risk with this approach is if the TC system fails for some reason (runs out of acid). Then the PH might get fairly high before you notice and there could be scaling. Given your fairly low natural aeration rate, that isn't likely to be a problem so long as you look at the TC system display regularly to see if a problem is indicated.