New Pool Owner - Tested Water, Need Help With Fix

[bbq]

New pool owner here. I've been reading and researching a lot but need some help.
I'm estimating the pool is 20,000 gallon plaster. Pentair CCP Filter. Has a inline chlorinator. Previous owner used PoolBrand tablets.

It has algae forming.
With the TF-100 Test Kit I got the following results:
FC 0
pH 7.5
TA 70
CH 775
CYA 50


So I definitely need to add some bleach. Calculator says 121oz of 8.25% to raise to 4 or 241 to shock. 75oz of baking soda to raise TA

My big concern is how did the CH get so high and do I really need to drain half my pool?
Help! What is my best course of action?

 

[JohnT]

Welcome to TFP!

If your fill water has high CH levels, your pool CH will increase as you replace water that evaporates. Powdered shock often contains calcium. It can also be leached out of your plaster.

To reach shock level, you will need more than 240 oz of 8.25% chlorine. Your shock level is 20ppm. One gallon will raise your pool's chlorine level by 4.125ppm, so you will need about 5 gallons to reach shock level.

 

[bbq]

Thanks JohnT,
You're right, I read 8ppm by mistake.

Is the high CH a major concern? Is it worth draining and filling (assuming my fill water has a relatively low CH)?

 

[JohnT]

High CH can cause hard to remove calcium deposits on pool surfaces. I'd test your tap water to see where you stand.

 

[Kiss4aFrog]

Welcome to the forum

Hopefully you aren't using that inline chlorinator any longer. You are at the high end of the CYA range and every tablet adds more CYA that just keeps adding up. The FC in the tablet gets used up but the CYA just keeps building. That's why we recommend using liquid bleach to add chlorine as it adds no CYA along with it.

With a CYA level of 50 you should try to daily maintain your FC level at 6 and never let it get below 4 as shown in the chart - - > http://www.troublefreepool.com/content/128-chlorine-cya-chart-slam-shock

As for the CH you need to test your water to see if it's coming from something added to the pool or it's the fill water itself.

Remember it's much easier not to add something to the pool water chemistry than it is to get it back out.

 

[Wildcat]

IMHO, 50 or even 70 CYA may not be too high in sunny climes. The need for protection from the sun for CL is much greater in the Southwest than the upper Midwest. Geography plays a role in normal chemistry levels. What is good for one area may not be optimal for another.

 

[zimm]

I wouldn't worry about the TA yet. Get the FC up pronto! CYA is maxed, so no more tri-chlor. You can test your tap water with the TF-100 and see what CH levels you get. You might have really hard water.

 

[pwrstrk]

I see no mention of the SLAM Process. If you have algae forming you need to SLAM the pool. Follow the process to the T.
After the SLAM is complete your FC level range should be a target of 8 and never below 4. With targeting 8 that will give you more wiggle room so you don't fall below your min of 4. ?

 

[bbq]

Hose water has a CH of 125.

 

[bbq]

Starting the SLAM now.

 

[pwrstrk]

Good job !

 

[Kiss4aFrog]

Since the replacement water is only 125 that high CH reading is likely from the PO adding something better left out of a pool Once it's free of algae you might need to do a few drain and fills. For now just concentrate on the SLAM and when it's done you should make sure you keep pH and TA controlled.
Good reading on CH - - > http://www.troublefreepool.com/threads/52661-Calcium-Hardness-increasing

IMHO, 50 or even 70 CYA may not be too high in sunny climes. The need for protection from the sun for CL is much greater in the Southwest than the upper Midwest. Geography plays a role in normal chemistry levels. What is good for one area may not be optimal for another.

You are absolutely correct and it's why TFP asks posters to add their location to their profile as location is a factor. In AZ or TX I'd want a lot more CYA then I have in mine here in WI. When the pool is sparkling blue and the SLAM is done it's something to consider.
If I'm going to need to SLAM my pool as BBQ is doing now I would want that CYA as low as possible with just enough protection to keep it from burning off in the sun. That way I can use the least amount of bleach ($$$) to do the same work. Usually that is around 30 in a perfect world but with his at 50 I wouldn't want him to raise it now and just cost him more money in bleach and force him to maintain a higher SLAM FC level.

Why raise the CYA to 60 or 70 and make the SLAM FC level 24 or 28 respectively when at 50 you only need to add enough bleach to reach 20ppm FC