New liner - start-up metals info needed

[ivyleager]

Just switched out my 16yr old 20mil liner last week for a new 28mil as it was quite faded and had some water under it in deep end. I was able to fill my pool 16yrs ago from well and never had issues until years ago when I had staining; treated it and kept it at bay for the most part. No staining on liner or steps last year but when I opened pool this season I noticed steps were not pearly white, ever so slightly discolored. Pool guy brushed some Metal Magic on them prior to liner install and it was gone. He also changed my filter sand (never been changed) and it was very reddish/brown. Said that was iron. He is pretty sure my well water has iron. Maybe I do, but I do not have iron staining in my toilets or bathroom sinks, nor on my washed clothes.

So here I am, again I filled pool with well water. Slow and steady took 90+ hrs ~20K gals. No stains currently so I want to prevent at this point, right? I previously used Jacks Magic Pink bottle. I see many newer posts mentioning ProTeam Metal Magic.(I also have CuLator packets I have always used, 3-4 packets per season).
Willing to do whatever it take to prevent further staining.

Current chems:
FC 3
pH 7.5-7.8
CYA 30
ALK 140 - tap water is also 140 (As an aside, for the life of my pool I've struggled to keep ALK >70, and I add quite a bit of fill water. Hoping this goes down with rainfall).
*CH low.., no clue (I hate this test. I rarely turns a true red, just a faint hint of pink, so it's low end of range. It take about 10-15 drops to even appear to change color a smidge and never changes to a blue.) *I've been reading up on more current forum posts about need to maintain Ca+ levels in presence of metals in water regardless of pool surface. Need info.

My pool guy has Metal Magic on hand so can pick some up. He said about 3-5oz weekly for my pool. ProTeam website doesn't indicate maintenance dosing.

My specific questions are:

1. My chemistry looks okay. ALK high but not danger level, right?
2. Do I need to raise my Ca+ to help with sequestration?
3. Do I need to lower my pH when adding sequestrant?
4. Is there currently a consensus that MM is a better sequestrant? And what is the maintenance dose recommendations?

Also, please add anything relevant that is not included in my questions above. I'm here to learn.

Thanks Mods!
-Cary

 

[justinc]

Hi Cary,

The sequestrant that seems to be popular around here is Jack's Magic (whichever variant is designed for your pool surface/situation). I use The Blue Stuff for my pebble pool and it works well. Usually you have to give a large initial dose and then keep up the levels in the water by doing weekly additions. The bottle should have full directions and dosing based on the volume in your pool. As far as your test results are concerned, your chlorine level is low compared to what is recommended. I would encourage you to check out the Chlorine/CYA chart in Pool School. Your pH is fine. Your CYA is fine, but you may want to add 5 to 10ppm so that you don't go below 30. You will find you lose around 5ppm CYA per month from splash out. Your alkalinity is not anything to panic about. With higher alkalinity, you will notice your pH rise. You can also increase the rate of pH rise through aerating the water (waterfall, jets pointed upward) and then lower it using muriatic acid. This will also lower your total alkalinity. You can stop aerating and manage pH as usual once you get closer to 80 or 90 on your total alkalinity. As far as calcium hardness goes, this really isn't much of a concern in a vinyl pool; however, you may want to keep your calcium hardness around 100 to 150 to prevent foaming (especially if you have an attached spa).

 

[Texas Splash]

Cary, so yes, wells typically have an elevated iron content. Sounds like you just got lucky for a long time. For your questions:
1 - TA is elevated. Problem with that is it will tend to pull your pH up as well. An elevated pH is bad for iron water. Makes it want to precipitate out and stain. So I would lower the pH which over time should also help to lower the TA. I'd say get the TA eventually down to about 70 or so and keep the pH from going over 7.4-.7.5.
2 - While CH is typically of no value in a vinyl pool, you may be in a situation where a CH of at least 50-100 might help to prevent staining. I can do some more poking around on that one.
3 - Just follow the instructions on the bottle, I don't recall. But as noted above, you will want to keep the pH on the lower end of the 7s anyways.
4 - Any sequestrant can work, but sequestrants based on HEDP, phosphonic acid, or phosphonic acid derivatives are generally the most effective. Rememebr they are temporary, so you'll need to replenish periodically.

Lastly, avoid algae at all costs. Maintain a good FC/CYA balance as noted on the FC/CYA Levels. A lower FC is like a lower pH in that it does better for the iron. If you have to SLAM to remove algae, the higher FC level will tend to make the iron angry. But always watch the FC/CYA Levels.

 

[ivyleager]

Hi Cary,
Your CYA is fine, but you may want to add 5 to 10ppm so that you don't go below 30. You will find you lose around 5ppm CYA per month from splash out.

Thanks! I'm currently using pucks for the first month or so to get my CYA up a little higher, to 40ppm. I dropped a few extra pucks in to raise the FC to 4.

 

[justinc]

Thanks! I'm currently using pucks for the first month or so to get my CYA up a little higher, to 40ppm. I dropped a few extra pucks in to raise the FC to 4.

Just FYI, one eight ounce Trichlor puck will add about 1.5ppm CYA to 22,000 gallons. This should give you an idea of how many pucks you can get away with using (about 13) before your CYA level goes over 50. Once you hit 50, switch back to using liquid chlorine.