CYA and CH too high :: help please

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fscott

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Feb 19, 2010
25
San Diego, CA
Hi everyone

My husband and I have just bought our first home in San Diego with a pool. I have to tell you I'm very excited to have found this forum because I'm a scientist and love the concept of water testing and managing the pool on our own with bleach, baking soda and borax...

We've been in the place for 6 weeks and the pool looked in good condition when we moved in. It had been kept uncovered with the chlorine pucks in a floaty-thing. I had a pool guy give me the run-down on things - said the chlorine, pH and TA were fine. We then kept it covered for a few weeks which, may have been a bad idea as the pool cover was NASTY - lots of black mold. Put it on anyway not knowing any better. Now we're ready to take control of this thing.

I think it is a plaster pool - kind of rough surface. It does have some brownish patches on sides and floor but they don't seen to scrub off or feel slimey. This morning I noticed a small group of black spots on the steps which are underwater. These also don't feel slimy and I can't scratch them off with my fingernail. Unfortunately we haven't owned it long enough to know what "normal" looks like for this pool, and I can't say whether these black spots are new or not.

There is also a white ring on the tile at the water level - I assume this is calcium deposits

I've removed the pucks and been using bleach for the last week. My TF100 arrived today and have run the numbers...

FC 4.5
CC 0.5
TA 110
pH 8
CH >800 (is this possible???)
CYA 100
Borates ? (test strips in the mail)

What now? I have muriatic acid and chlorox but what to do about the CYA and CH???

With water restrictions in San Diego we'd been catching the water off the roof after rains and saving it in plastic trash cans - can I use this in the pool?

Thanks and I look forward to your advice.

Cheers,
Fiona
 
fscott said:
With water restrictions in San Diego we'd been catching the water off the roof after rains and saving it in plastic trash cans - can I use this in the pool?
Click to expand...
You can -- but would first advise testing that water in the same way you test the pool water to know what's in the water you want to add... as a scientist I'm sure you can appreciate this! :-D If you decide to go this route you'll want to add extra chlorine as a precaution against latent algae in the cans. The bigger problem, however, is that you'll find that you will need many more trash cans of water than will have been stored to displace pool water that contains those very high CYA and CH levels. It's not unreasonable to think that you'd want to replace half of the water. If you end up having to fight algae, a lower CYA level will make the process easier and faster.

The high CH may have originated from the combination of city water containing a high level of calcium and several seasons of evaporation. The high CYA almost certainly comes from the pucks that have been used to chlorinate the pool. In your situation, I'd definitely recommend retiring the pucks in favor of admittedly less convenient liquid chlorine or bleach. Don't add borax or worry about the level of borates until you have your pool water where you want it.

If you have or suspect algae or mould, you should read up on Defeating Algae and ready yourself for the season by scrubbing and oxidizing the mould and other organics on the pool cover as best you can. There are lots of other good articles to be found in Pool School that will also prove helpful, including one that can help you diagnose stains.

BTW The recommended minimum level of chlorine for a pool without an operating SWG is about 7.5% of CYA -- quite a bit more than what's in there now.

Welcome to the forum :) and congrats on your new home/pool! Consider posting a few pics of your pool to get some opinions regarding the stains.
 
Many roofing materials can contaminate the water, so that it is no longer suitable for use in the pool. Asphalt roofs, which are quite common, "leak" petroleum products into the water, especially in the first few years after they are installed. Metal, plastic membrane, and tile roofs are fine for water harvesting, especially if you keep them fairly clean.

You should get your PH down soon, as you are at risk for calcium scaling if you don't (assuming the CH reading is correct). The three primary factors that combine to cause calcium scaling are high PH, high TA, and high CH levels. Reducing CH is the best thing to do, but that will be difficult if you have water usage restrictions. When you can't reduce CH, you need to keep PH and TA on the low end of their ranges to compensate.
 
Fiona,

Welcome to the forum. Reinforcing what Greg has already said, you will need to drain water.....a lot of it. I would do that first to get the CYA down around 50ppm....about a 50% drain. It's best to do that in two stages.

If you simply cannot do the drain, post back and let us know. You can manage where you are but it will be very troublesome. Nevertheless it is doable. if you make that decision, you'll get (and need) lot's of help.

Don't worry about all the organic stuff until you make the drain decision.....chlorine (and lot's of it) will clear the pool.
 
Ok, thanks for the advice.

So I a dded a gutload of bleach this morning to bring up FC to >7...need to buy shares in Chlorox...also added muriatic acid to bring down pH to 7.4.

Regarding the pool drain issue...The Husband Unit is "anti" the pool drain and fill. We're eco warriors at heart! I don't even know how to drain the thing - is it through the same outlet that you backwash?

Will post pictures of stains on the weekend and try the Vitamin C vs chloring puck test. Wire brush is ordered just in case...*sigh*

Cheers,
Fiona
 
fscott said:
Ok, thanks for the advice.

So I a dded a gutload of bleach this morning to bring up FC to >7...need to buy shares in Chlorox...also added muriatic acid to bring down pH to 7.4.

Regarding the pool drain issue...The Husband Unit is "anti" the pool drain and fill. We're eco warriors at heart! I don't even know how to drain the thing - is it through the same outlet that you backwash?

Will post pictures of stains on the weekend and try the Vitamin C vs chloring puck test. Wire brush is ordered just in case...*sigh*

Cheers,
Fiona
Click to expand...

On mine I have a water hose attached to my plumbing that I turn on the nozzle and it starts to drain. This is a very slow process for me and would take all day to drain out all the water. Now backwashing will get rid of your water a lot quicker and will help clean out the filter as well. This is a good way if you need to backwash to get rid of a lot of water. Also what type of filter do you have sand, de, or cartridge. You can get this information more than likely off of the filter.

Welcome.
 
I don't mean to keep bringing bad news....really :oops:

You need a lot more chlorine....a lot more. If your going to keep your current CYA level of 100(+) the minimum to keep your pool should be around 8ppm....constantly replenished so it stays between 8-12ppm at all times.

Now, to clear the algae in your pool and get your water clear, you'll need about 25-30ppm and you'll need to keep it at that level thru constant replenishment until your pool is completely clear.

Look up in "Pool School" (upper right) and then look for the CYA/chlorine chart......it'll confirm those numbers.

Also, go ahead and get muriatic acid in your pool to lower the pH down to around 7.2 - 7.4. That should stay stable once you get it down there. You will need to keep it in that lower range because of the high CH.

Once your pool gets clear, you will still have to maintain your FC up around 10ppm because of the high CYA. Never use pucks in the pool as they will only add CYA....calling for even more chlorine.

This is still doable but you will need an amazing amount of chlorine to allow for the very high cYA
 
Another idea adding to David's solution to draining: a submersible pump.

I sure understand your reluctance to drain water, but if you consider the amount of hypochlorous acid that must be in the pool to attain satisfactory levels of sanitation and oxidation (see duraleigh's post, above)-- not to mention all of the Clorox shares you'll be invested in by the end of year -- it makes the most sense.

This won't be a recurring problem if you maintain a low(er) concentration of CYA... 20-30 ppm for non-SWG; 50-60 ppm if your system uses a SWG to chlorinate.
 
If I am not breaking board rules, I might suggest that there is an alternative to draining the pool to address the high CH levels. PM me if you wish, or check my signature for more information. 800 CH is very high, and you do need to address it, as others have said.

Mods-Please delete my post if I am not allowed to make such a suggestion.

Edit: Instead of replacing water you could get a reverse osmosis water treatment, which will lower both the CH and CYA levels. If you PM me I can recommend a company in your area. (Thank you, Jason :goodjob: )
 

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I don't want to push an agenda here, but chances are that there will be few folks with any hands on experience with this type of system. While R/O is not new by any means, the use in swimming pool application is. This alone limits the exposure to a handful of people (me being one of those people :cool:).

I would think that your concern about lowering the CYA if you utilize R/O is valid, and that a reputable company would guarantee a reasonable level upon completion of treatment, or the service would be free.

I'll keep watching this thread for input as well! Should be a good one, and an opportunity for all of us to learn something!
 
Reverse osmosis works. RO lowers all of your levels, not just CH. In most cases, you will need to add chemicals to get some of your levels back up, though often the RO company will do that for you. Prices vary by region. In some areas it is cost competitive with a drain and refill, in other areas it is more expensive.
 
Yes, RO removes everything: TA, CH, CYA, Borates, Salt, iron, copper, magnesium, algaecide, sequestrant, phosphates, everything. The levels are all reduced by the same percentage. The percentage removed is adjusted based on what your goals are. Typical percentage removed are around 70% to 80%, though treatments can range up to 95% or so. Higher percentages may cost more, depending on the company. RO can never remove 100%.

RO treatments are not currently available in most areas. RO is most commonly offered in extremely arid areas with high CH fill water. An RO treatment is not normally something you can do yourself. The equipment required is quite expensive, and you only need it for a few hours. Therefore RO is normally done by service companies that spread the equipment investment out across many different customers.
 
duraleigh said:
Fiona,

Welcome to the forum. Reinforcing what Greg has already said, you will need to drain water.....a lot of it. I would do that first to get the CYA down around 50ppm....about a 50% drain. It's best to do that in two stages.
Click to expand...

Why two stages?

I’m assuming from the water restrictions that her water table is probably too low to worry about floating the pool at 50% full. It seems to me that draining and filling 25% twice would only remove 43.75% of the CH & CYA because 25% of what you pump out the second time is fresh fill water from the first round.
 
Why two stages?
Click to expand...
Just staying on the safe side for the very reason you suggest....water table. without being 100% positive of the water table, I am suggesting two bullet-proof stages and sacrificing the 7% of exchange.

Additionally, it's likely a little easier to do two smaller drains than a single large one for possibly inexperienced folks.
 

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