My new plaster pool is COVERED in green stain..

[hausfrau]

You are so nice.

I have actually asked about a more high tech kit for testing my water and was told there isn't really anything better than the strips I am using. Hmm...a plot here? I do not want to be at the mercy of the pool stores...I am a nice calm person, but I am getting rather riled up as each time I go in, I get a different opinion.. Iwas wondering...should I have my well water tested-the water that the pool is hooked up to?

I will take your suggestion...and thank you for it. I am going to take a pool class that Self-Chem offers...but will take some of it with a grain of salt (no pun intended) as they probably want us to be dependent on their chemicals! I am also brushing the plaster more right now in hopes that it will inhibit the growth too. We are having lots of storms now (near Austin, TX) so I am sure this will throw everything out of wack too.

Please wish me luck! I'll keep ya'll posted on my pool nightmare!

[waterbear]

You are so nice.

I have actually asked about a more high tech kit for testing my water and was told there isn't really anything better than the strips I am using. Hmm...a plot here?

As someone who has worked in pool stores I can tell you that the answer is probably yes. We did not carry decent test kits (except for the K-2005 we stocked in units of 1 for the condo associations) so people would come to us for water testing and we could sell them a lot of stuff!
As far as test kits, get yourself a Taylor K-2006 (not the K-2005). It will save you a lot of time and money in the long haul!
You might have to order it online. Here is a link for Amazon:
http://www.poolforum.com/pf2/showthread.php?t=10006
While this is not the only place you can get it you will be supporting Pool Forum by ordering from this link and help keep it going.

[hausfrau]

Just for the heck of it, I had our well water tested to check on metal in the water. it came back very low for copper...0.2. So yes, algea. Now, to get a decent test kit (as suggested on this site) and buy some bleach...will keep ya'll posted!

[hausfrau]

Thanks for the good advice!

Muriatic acid seems to have done the trick in our spa. We turned the spa off and added a muriatic to the water. Let it sit for an hour. It really cleaned it up. The concentration would have been about .2% for total volume.

A few questions:

1. What is the maximum concentration of mutriatic acid that can be safely used in a plaster pool? (14400 gal)

2. Can the PH be lowered a significant amount for a period of time then raised to normal levels without potential damage to the plaster?

3. Should the DE in the filter be changed or backwashed to eliminate any residual algea?

4. As an aside, to eliminate the possibility of metal staining, will muriatic acid also remove Cu or other metals from the surface of the pool?

Again thanks for the help. Big learning curve for us on this!

[hausfrau]

My earlier posts have been about the dark green algea all over the plaster of my NEW pool. After doing a test in the hot tub only...muriatic acid made it go away. Chlorine has not worked (old theads will give more detail), but no, it is not a metal stain... so

A few questions:

1. What is the maximum concentration of mutriatic acid that can be safely used in a plaster pool? (14400 gal)

2. Can the PH be lowered a significant amount for a period of time then raised to normal levels without potential damage to the plaster?

3. Should the DE in the filter be changed or backwashed to eliminate any residual algea?

4. As an aside, to eliminate the possibility of metal staining, will muriatic acid also remove Cu or other metals from the surface of the pool?

[hausfrau]

We added the muriatic acid to the water this time...rather than draining and spraying. It is snow white again.

[waterbear]

Muriatic acid is not killing the algae. it is removing a layer of plaster from your pool and that is not always a good thing.
Extended periods of pH below 7.0 are hard on pool equipment at best and outright damaging at worst.

If you have a heater I hope you bypassed it because heat exchangers are easily damaged by low pH. The result of damage to a heat exchanger is usually green hair and copper stains on the plaster--out of the frying pan and into the fire so to speak.

There are methods for doing a "no drain acid wash" which is what you have attempted but they include monitoring the pH and bringing the pH and TA back up once the treatment is finished. They should not be attempted unless you have both acid and base demand tests and access to the large amounts of baking soda, soda ash, and/or borax that is going to be needed to stop the process. Also, a pH testing method other than phenol red is a good idea so you know just how low the pH really is. Best choice is a calibrated pH meter (expensive piece of equipment).

While you may have removed the stain you have not killed the algae.
to answer your questions as you numbered them:

1. you do not want the pH below 7.2 for an extended period of time! Amount of acid that will lower the pH depends on your starting pH and TA so it is impossible to give a set amount.

2.In a word, no.

3. Algae is not going to be your problem now. You have probably elevated your calcium hardness at this point by dissolving plaster. Just clean the filter like you normally do.

4. Muriatic acid is used to remove metal stains when other methods fail. Certain copper stains (the black ones) are very difficult to remove and acid washing is often the only recourse. Realize that it removes the stain by removing a layer of plaster. You can only do this so often before you need to re-plaster the pool.

Also, acid washing is the only thing that can remove scale (calcium deposits). Realize that calcium is also a metal.

Finally, Muriatic acid does not kill algae, chlorine does. If you had a bit of patience and persistence you would have eliminated the problem without causing damage to your plaster.

Hope this is helpful and gives you something to think about.

[sunofthebeach]

do you have any of the"algae" left? Can you post a picture?

It is hard for me to believe your pool installer did not know what algae looks like.

I do like your style hausfrau, charge forward and try anything and everything.

If it were me I would go out today and get a test kit, even if it is a $5 chlorine and PH kit from Walmart. I have rough, pitted in some areas plaster because I did not pay enough attention to the PH and Calcium.

If what you really have is Algea, you are going about it wrong goofing with the muratic acid. I am sure acid will kill algea, but you probably harming something else.

[hausfrau]

Waterbear & sunofthebeach. Thanks for your posts. I should clarify. What killed the algea in the spa was not the acid but a shock to the spa. I isolated the spa from the pool and elevated the Cl enough to kill it then lowered the PH level to 6.5 for 4 hours. Not sure but I believe that the lower PH and short time period should not have attacked the plaster agressively. After the soak I purged the Spa. The spa feeds the pool. (500 gal into 14400 gal). I did not drain from the spa only from the pool so 6.5 PH water never touched the heater. Test strip shows Ca at normal levels for our water after 16 hours of circulation. Testing for Cu in both pool and supply show very low levels.

After the stain removal step. I circulated the pump for three days and the algea returned leading me to believe that a high sustained Cl level is needed to truly rid the pool of algea. As for the staining more than likely we will see what happens after a week or so. I purchased a test kit to get a better testing capability than the strips.

per an earlier post i read a sustained level of 25ppm is needed for shock levels. Any ideas on time period?

[aylad]

Maintain shock levels until the pool clears, the CC goes to less than 0.5, and you're not losing any chlorine when comparing test results from testing at sundown and again in the morning before sun hits the pool.

Janet