SWG and shocking

Hello all... this is only my second post and I hope its worthy:o

I have a SWG in my 20,000gal plaster pool. I've been very happy with all the normal benefits of a SWG, even if I do have to keep adding Muratic Acid regularly. My questions...

When I need to shock, is it ok to use Di-clor instead of bleach? Since I have a SWG the Cya levels should not be a problem, and I can just throw in a couple scoops in stead of luging around bleach bottles.... right?!? In other words... are there other downfalls to using Di-clor?

When shocking with a SWG system, should you shut the SWG off till the FC levels drop or just let it keep running, which would take longer for the levels to drop.?

Thanks....Dave

So long as you don't add acid and Dichlor at the same time it should not be a problem. I personally prefer bleach or shock.

There is no need to shut off the SWCG. The Dichlor or bleach is there for upsets only.

Pat

If your SWG is operating properly you probably will have very little need to shock the pool. Dichlor will cause your CYA levels to rise since it is stabilized chlorine. If your calcium levels are not too high and your TA is not high you can also shock with cal hypo and if you don't mind throwing money down the drain you can shock with lithium hypochlorite. Both of these are granular also. The advantage to shocking with bleach is that you are putting sodium hypochlorite in the pool which is exactly what your SWG is producing .

The main reason I can see for shocking a SWG pool is if you need to shock the pool itself such as if you see algae growing on the walls or something. The water is seeing high enough chlorine levels as it passes through the cell to break down any chloramines in the water, but the pool shell itself never sees Cl levels above the residual you maintain. Textured surfaces such as pebble are probably harder to see the small algae spots if they start, and harder to kill all the algae in the nooks and crannies between the pebbles. I personally use bleach to shock. Di-chlor is not as fast-acting and it adds CYA

algae will start growing in the water column before it attaches to the walls of the pool. If you are getting algae growth with a SWG then something is not operating or set properly or your Salt, pH or CYA are not at the proper level.
my 2 cents!
I can see the need for shocking if you have has a party and the pool has has a lot of use or if a kid has had an accident in the pool, in which case I would use bleach,but otherwise I firmly believe that a properly set up and maintained SWG pool will not need to be shocked!

My pool has been running at 4 ppm FC as maintained by my SWG and about 30 ppm CYA, my pH is 7.3. My pool water has always been crystal clear for almost 2 years and counting, never even a hint of cloudiness or algae in the water. Since early this spring, I've been scrubbing off small spots of green algae from my pebble-sheen mostly in the curve where the wall and floor meet. I've been finding 2 or 3 spots a week that want to grow. If I scrub tham well enough, they don't seem to come back, but new spots show elsewhere. Right now I'm bleach shocking the pool to a little over 15 ppm Cl since we're going away for a few days. After I get back I'll have a pretty good idea whether the shock has any effect on the algae spots returning.

I seem to remember Ben's pages saying somthing to the effect that certain types of algae would grow quite nicely in 5 ppm Cl, and that Shock levels for at least 4 hours were necessary to get rid of them for good.

Thanks for the input.

Waterbear, I have CC of 1, but CYA of 0. PH and ALK are fine. Are you saying that when I get my CYA up to 60 or so that a FC level of 5 will take care of the CC, or will i need to shock to get rid of the CC initially? Of course I will check it once the CYA gets to a normal level, but I'm just curious.

Algae starts to grow in the water column before it deposits on the walls of the pool. The SWG is constantly superchlorinating the water that passes through the cell and if you have balanced the pump run time and cell output it ususally takes care of it. You do need to keep tabs on your pH....it will constanly be climbing and that reduces the ability of the chlorine to sanitize. Many people with SWGs get lazy about keeping the pH in line and let it drift up high (around 7.0 to 8.0) and then wonder why they get algae or their FC is always low. I have also seen people that run their CYA low and they also run into problems. Most of the SWG manufacturers seem to recommend 60-80 ppm CYA and from what I have seen testing water all day the salt pools with correct CYA and pH kept in the 7.2-7.4 range seem to do the best and have very few problems.
Just my 2 cents!