Help With Green Swampy Pool

by Tom

I have a 33,000 gal inground pool and having a problem with a swamp after cover removal this year. We had a warmer than normal winter and may have been a factor to my current problem.

I shocked it with 6 lbs of cal-hypo and green to clean 4lbs. It has gone from dark green to a lighter green but that is all for the past 48 hours. I use a Pent-Aire FNS+ De filter but running it on filter and my pressure goes up to 20psi in no time and have to back wash is. I did I think get somewhat smart bu taking the cover of the filter off and spraying it off just to save some water. Added more DE and ran it again but to re-clog the filter again.

My readings are 0 free chlorine ,10 TCL, Alk 60, PH 8.2 and hardness is 100. I never had a problem like this before and need help.

I know the pool who build the pool is always out to make a huge profit but I am not sure what they say is truthful but I will do what ever it takes to make this pool back to it's old self.

I blame myself for this because I have in the past used a couple of gallons of liquid chlorine during the winter with algecide per month and have little problems opening up.

I hope you can help me with this problem or lead me in the right path that will correct this.

Thank you!!!!!!!!!!

Tom Donahue

Thanks for the question Thomas

Don't worry because I've cleared up many pools like yours on my route in Arizona. I promise it's not all that bad. I've scooped out of pools dead dogs, cats, birds, chickens, snakes, rabbits, ducks, cows, horses and a bunch more.

Thanks for the readings. It helps out alot. One thing that is missing is the cyanuric acid level (CYA). This is critical to know if you should shock the pool or need to do a partial drain and refill. Normal range is between 30 - 50ppm. If it's above 70ppm or so, a partial drain is needed. If it's below 20ppm, then you need to shock with Dichlor chlorine. This is a stabilized form of chlorine. Once you reach the 30 - 35ppm mark, stop with Dichlor and go back to regular liquid chlorine. Get a tab floater, if you don't already have one, and keep it full of tabs. Don't put tabs in the skimmer.

Be careful when using Dichlor as it can get out of hand quickly. For every 10ppm of chlorine added with Dichlor, you'll raise the CYA by 9ppm. For every 10ppm of chlorine added with Trichlor tabs you'll raise the CYA by 6ppm.

Now for the total alkalinity (TA) and pH. Normal range for TA is 80 - 100ppm, 120ppm being the top. Yours is 60ppm so it's not too far off. One ot two little corrections should do it. It's 1.4lbs. of sodium bicarb per 10,000 gallons to raise the TA 10ppm. I'd suggest using 7 lbs. to start with. Pump off and add the bicarb in one spot in the deep end. Let it sit for 3 - 4 hours, then pump back on and circulate for 8 - 10 hours. Retest and make another adjustment if needed.

Pool Alkalinity

Total Alkalinity

For the pH, it's 12 oz. to lower pH 0.2 per 10,000 gallons. Start with 1 qrt. of muriatic acid and broadcast it around the perimeter of the pool with the pump on and water circulating. Brush the sides and bottom well. Circulate for 8 - 10 hours. Retest and make another adjustment if needed.

Do the pH first, then TA. Because you're adding acid it might have a small effect on the TA so keep that in mind. You may need to raise it 30ppm instead of 20ppm. This is were patience and consistency comes in handy.

Also, don't go for any pH or Alkalinity Up stuff. It's either sodium carbonate or sodium bicarb. which is baking soda. Go to your grocery store and get a large box or two of Arm & Hammer or a similar cheaper brand for 1/3 the price.

Swimming Pool pH Levels

Pool pH

Remember to allow for 1 full turnover of the water, not the 1 or 2 hours you may have heard. It takes a full turnover to get a correct reading. The chemical need to fully circulate through the system. This is about 8 - 10 hours.

If you have a plaster pool you can get some calcium chloride to bring the level up to 150ppm. It's 1.25 lbs. to raise the hardness 10ppm per 10,000 gallons.

Calcium Hardness

Calcium hypo has a pH of 12 so I'd encourage you to stop shocking with that. The pool pH is already high and if you continue to shock with cal hypo you're probably going to be fighting the pH. Shock with Dichlor and get the CYA to 30 - 35ppm, then switch to liquid chlorine.

Next is the algaecide. This is used for preventative maintenance only, not to get rid of already existing algae. You can use it to augment the chlorine shock in case the chlorine drops to zero, but please don't think that by adding an algaecide it helps get rid of the algae. It doesn't, regardless of what the guy at the pool store said. If you still want to use an algaecide, get a PolyQuat 60. Most others and the cheaper kinds have copper and metal fillers in them.

Keep filtering, backwashing, and recharging with DE. Because of the algae, the filter will clog quickly. If the pressure rises too fast it may be time to clean the girds and recharge with DE. I know it's a pain, I've done it hundreds of times, but it needs to be done.

The trick is to get AND keep the chlorine above 10 - 12ppm for a period of time. You'll need to manually dose the pool with chlorine to keep it at 10 - 12ppm. Make the adjustment at night, then retest in the morning. Be sure to have the pump running 24/7 and backwash once per day. You can go up to 15ppm, but no higher. Anything after that and you're wasting money and chemicals.

Green Pools

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Hope this helps and have a great Summer.


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