Help! Metal in Pool Water & Black Algae Problem

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S

saguaro

0
Mar 23, 2015
6
Phoenix
We are in need of help! We are new to pool ownership and discovered our pool has terrible water, including copper & iron. We have black algae, as well. The local pool store (who tested our water - I have a Taylor Technologies complete kit on order) recommended we have it drained and acid washed. I am hesistant to proceed with acid washing because I have no idea when the last time the pool was resurfaced (or if it ever has been).

Here's a look at our numbers:
FC 0
TC 0
CYA 110
TA 100
pH 7.0
Base 25
Copper 1
Iron 1
Pho 500

We have a 10,000 gallon plaster pool, with chlorine as the sanitizer.


My question for the experts is:
What would you recommend to get our pool into safe swimming condition?

'
 
Welcome to TFP! :wave:

Your first step should be to dig into some of the articles on this site, in Pool School. Specifically, I'd start with ABCs of Pool Water Chemistry.

If you feel that the methods taught here on this site are for you and are willing to educate yourself and take control of your own pool, then you're half way there.

Specifically what kit do you have on order? If it's the K-2006, then you're off to a good start. It doesn't have the best value for your money for reagents, but it has all the tests you need. I would have recommended the TF-100 http://tftestkits.net/TF-100-Test-Kit-p4.html with the XL option, because you're going to be SLAMing your pool. The K-2006 will get you started though.

1 - Test your water with your own test kit once it arrives. It's going to give you more reliable results than the pool store. Post those results when you get them and we'll help you from there.

2 - If your CYA is actually 110, your first priority is to lower that to a more reasonable level, such as 50-60 ppm. The lower the better when you need to complete a SLAM but your CYA after the SLAM in Phoenix is likely best in the 40-70 range, depending on your chlorination type.

3 - Add the details of your pool to your forum signature. You can do this by clicking Settings, then Edit Signature and make sure to click Save after you've added the details. Check out other people's signatures for ideas. The important things to have in there are your pool surface, volume, filter type and any other details you know. Also, most importantly let us know what kind of chlorine sanitation you're using. Are you using chlorine tablets? Liquid chlorine? A salt water chlorine generator? Of those three chlorination methods, tablet are NOT recommended for long term use on this site. Each tablet adds CYA to your pool which many times leads to unmanageable CYA levels. Liquid chlorine (aka Bleach) or SWCG is recommended.

Also... is there evidence of metal staining? You may have high/elevated metals but if there is no staining... Nothing to worry about, yet. You may not know you have staining until you get the algae cleared up.
 
Thanks for the welcome and suggestions, JV Train. I have been reading the TFP site thoroughly. The previous owners used chlorine tabs, and we continued doing so ... not realizing they were adding the problem and not really working. Yes there is evidence of metal staining. There are rust colored spots in a few places on our steps and some black dots that are not brushing off with a metal brush. They appear to be different from the algae, which is brushing off of the water line and corners.

We have no idea when the water was last changed; the pool is 20 years old - so we're leaning toward draining and refilling. However, I am also concerned about the potential for plaster cracking. I don't know at what temperature that can occur, but it's already getting warm in Phoenix.

I ordered the Taylor K-2006 kit because I could get it from a local supply store more quickly than ordering online. It will be in tomorrow and I'll post results after testing. And I'll get the details of my pool added later. Thank you again, for the welcome!
 
The possibility of draining the pool safely without risking cracking plaster or blowing out walls is subject to several conditions.

- Is your local water table low? My guess is that the water table is low in Phoenix but it may not be in your specific location. That is... the higher the water table, the more likely it is that there is alot of hydrostatic pressure on the outside of your pool walls. If the water table is low, there will be less. Lower water table = lower risk of cracking when pool is drained.

- Can you cover the pool while refilling or refill very quickly overnight? If you drain the pool, it's most at risk for damage on the plaster surface due to high temperatures, made worse by direct sunlight and dry air. If you can cover the pool while draining and refilling, that helps alot to avoid issues.

As far as the metals issue goes... you might want to think about doing an ascorbic acid treatment first then draining the pool to attempt to remove the stains then remove the water that now has the metals dissolved in it. I'm not an expert on plaster surfaces or this metals treatment so perhaps another expert can chime in. I'm not sure the AA treatment will work as desired in pool that has a current algae problem. This is a good thread on the AA treatment process. http://www.troublefreepool.com/threads/2129-Ascorbic-Treatment-to-rid-Pool-of-metal-stains
 
If you rent a submersible pump from Home Depot in the afternoon, you could have your pool 50+% drained in a few hours and then get it started refilling over night. If you are concerned about the plaster you could just wet it down after the sun starts beating on it if it is not full.

Usually you want to treat the algae problem, then the metal problem while using some sequestrants. Reason being that higher FC levels required for the SLAM may reintroduce the metal staining. BUT, since you are going to drain, doing the AA first might allow you to get more of the metal out of your water when you partially drain.
 
Right. In your case it would be worth trying the AA treatment at your current readings. Then when the metal stains have dissipated, drain the pool. Either a partial drain or as much as you're comfortable with. Then refill and deal with the algae with the SLAM procedure.

Hopefully doing things this way will remove most of your stains and a good deal of the metals that the AA dissolved in the removed water.

Sent from mobile device. Beware of brevity and spelling errors!
 
We ended up draining the pool and are currently refilling because the test kit I have confirmed the CYA was well over 100 (probably close to 200).

My next question is, what order (and how quickly) do I add chemicals? Do we need to run the filter for awhile before testing the water? Do I start with the pH and adjust it before adding CYA and clorinating? I've looked at the TF site, but don't clearly see instructions on how to add chemicals to new water. Thanks in advance!
 

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Use PoolMath to calculate dosages to reach your desired targets.

You need to get CYA dissolving in socks on the skimmer. Keep the FC up around 2ppm until the cya dissolves and then raise the FC to the appropriate target level. See the FC/CYA chart in Pool School.

Btw, for the FAS-DPD test, use 10ml of water so each drop is 0.5ppm.
 
Great! Thank you.
So - CYA first and initial chlorine ... When do I adjust the pH?
Thanks for the tip on the FAS-DPD test. I had trouble getting the powder to dissolve, so I ended up adding water to the 25ml mark. Do I need a SpeedStir to get it to dissolve more easily?
 
You can do the pH now too, only need about 30 minutes between adjustments.

As long as the water is a deep pink to start with, don't worry about extra crystals. You can not use too much powder, but too little can lead to problems.
 
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