My Ongoing War with Brown Water & Iron

[marygreencny]

This is our third summer with an inground 20k gallon pool. The first two years we didn't have this problem but this year we had to put a ton of well water into the pool (like half the pool water) since then, we have a constant cycle: shock pool, it's brown, flock it to get rid of the brown, vacuum it out, add more water (filtered now but that doesn't seem to be helping), then again we have to shock as algae starts growing and I'm told we have to shock the water regularly anyhow, then it's brown again.

We tried a metal sequestrant (two bottles of it), it worked, the pool was mostly clear, then we had to fill more water (we had a leak, it's found and fixed) and when we shocked it, it went brown (even though we have a filter), so I made sure the chlorine was 0 (which was weird as it was right after we shocked) and put in more Metal Out, but nothing happened, so today I add PH decreaser and still nothing, brown pool water.

On top of this, we had replaced the sand in our filter, about 6 weeks ago and when I try to backwash it's still clear. Although to be fair we gave up on the pool for a couple of weeks and weren't using the filter. We've spent hundreds on "opening" the pool this year and it's never been really clear yet. Any thoughts you can share to help me out?

 

[YippeeSkippy]

Hi there, welcome to TFP I'll try to address each problem you mention-
Yup, well water full of iron will make a pool brown. Chlorine seems to exacerbate it. One trick to use such as when topping off a pool is to fill a lidded bucket (like you see at Home Depot/Lowes) with polyfil and run the water thru there slowly into the pool. The polyfil can catch a lot of the iron. Another way is to add polyfil to the skimmer, as long as you don't block all water movement.

Metal sequestrants often "wear out" and need to be replenished. Tell us more about your pool and its equipment.

Why did you replace your sand?? Sand almost never needs to be changed (don't fall for it just cause a pool store told you to, they're out to make a sale). Good backwashing practice and not adding potions we don't recommend will help your filter work best.

How do you normally chlorinate the water?? Do you have a test kit- we need you to have one of the two kits we trust and can give you all the results you need:
FC
CC
pH
TA
CH
CYA

The test kits are either the TF-100 or the K-2006C. Either get that from www.tftestkits.net or poolsupplyworld.com (I prefer the TF-100, its $70 but will last you two years usually)

Maddie

 

[Shirker]

If you have high iron in your water you need to try to keep the water balanced without large swings in pH or chlorine. That means you need to test frequently (with your own test kit) and keep your chlorine in the correct range based on your CYA. If you keep it properly balanced you should never have to shock the pool. Each time you do shock you will battle iron coming out of solution.

 

[marygreencny]

Thank you both @YippeeSkippy and @Shirker

@YippeeSkippy Our pool is a vinyl oval 16x32, 3ft - 9ft in the deep end, we have a sand filter, 1 skimmer, 3 return jets.

The pool is brown now, I added decrease ph (the whole bottle yesterday) and it's still just under the highest color on the strip 7.8 I got more sequestrant today not realizing the ph is still so high, so I have to wait to get more decreaser, the chlorine is 0, even after the shock so I'm guessing it was non existent before.

We had replaced the sand because we couldn't figure out any other reason the water was so dirty it was the metal.

@Shirker Up until this point I've used test strips, but I'll look at the other test kits. We usually use 3in chlorine tabs. Where should the levels read for the chlorine? How often should I test? Can algae still grow if I don't shock it?

What should I do next?

 

[Shirker]

Where should the levels read for the chlorine?

The amount of chlorine you need is based on how much CYA (stabilizer) is in your pool. The higher the CYA the higher your chlorine needs to be to remain effective. See this chart.

Can algae still grow if I don't shock it?

Algae can not grow if your chlorine is in the target range based on your CYA. As long as you are in that range, there is not ever really a need to use shock.

How often should I test?

In my personal experience I only needed to test once or maybe twice per week. But anything out of the ordinary might require extra testing. Heavy rain, Hot sunny days, kids' have friends over, etc... But until the pool is really under control you should at least test for FC and CC daily.

 

[zea3]

When you have a source of fill water that is high in iron and having fresh water trucked in is not an option, you can filter out the rust that is turning the water brown. Use polyester pillow stuffing in the skimmer (keep the skimmer basket in place) to collect the rust. If you have an inline leaf canister stuff it lightly with pillow stuffing and use the manual vacuum to feed water into the pump. Every few hours turn off the pump and take out the dirty pillow stuffing and replace with fresh. The pillow stuffing can be rinsed out and re-used. Once you have filtered out the iron that has fallen out of suspension the pool should stay clear until another significant addition of iron laden water occurs.

Keeping the pH low (around 7.0-7.2) will help keep the iron in suspension. Keeping the CYA low so the chlorine can be kept low also helps.

Do not use flocc or any product that requires vacuuming to waste. Having to replace large amounts of water will just continue the cycle of chlorinating fresh fill water and having it turn brown.

 

[YippeeSkippy]

Use Muriatic Acid to lower pH when needed. Its cheaper, works better and faster and more predictable. Just stand upwind to it when using as the smell is kinda nasty.

Also...if your pool is plaster (is it?) dry acid is not good for it- the sulphates that the dry acid leave behind are bad for plaster.

Maddie

 

[marygreencny]

This morning I put the sequestrant in and the brown is gone but the pool is cloudy. Ph and chlorine are very low. Do I wait before slowly adding chlorine and ph?

 

[Shirker]

Do I wait

Chlorine needs to come up to your target range as quickly as possible (and stay there). Do you have a test kit yet?

 

[marygreencny]

I do have a kit. What’s the best way to increase chlorine without doing it too fast and causing the brown to come back?

 

[YippeeSkippy]

Go slow, one ppm at a time. Use PoolMath (either the phone App version or the web version found at the bottom of this page) to guide you on how much makes 1ppm.

Maddie

 

[Shirker]

Just be careful about going too slow. If you get an algae bloom then the SLAM level chlorine will cause more iron to fall out of solution.

 

[YippeeSkippy]

This may be one of the few times we suggest an algaecide as a preventative... Polyquat 60 type, no other.