I need a way to eliminate iron once and for all.

[TreeFiter]

I have a customer who has issues with iron staining in his pool. He never had a problem until last year. That is when he hired me. He thinks it is because his previous pool guy added water from his well to top off the pool.

Last season, I fought with the staining all season. I could remove the stains, but then algae would grow because of the low FC levels. Then I would SLAM the pool, and the staining would come back. This went on all season. So this year, he would like me to find a more permanent solution to the problem. Are there any options that will remove the iron permanently?

Has anyone ever heard of using an iron filtration system (Manganese Dioxide or Greensand) to remove Iron from a swimming pool?

 

[Donldson]

I use a greensand filter on our home water supply to remove hydrogen sulfide, it does remove iron but not all of it. I don't know how many gallons it can filter before requiring regeneration (or rather how much iron before saturation) but I imagine it would be a very long and water intensive process.

One idea JoyfulNoise (who managed to post at the same time as me, eerie) briefly mentioned before, Poolife released a product called NST, which appear to be a compressed cal-hypo tablet. If you were to raise the pH and then add these tablets to the skimmer, the high pH and locally high FC should cause the iron to precipitate out and then be caught by the filter. This is based on an idea by Ben Powell (he gets credit for the FC/CYA ratio and is essentially the grandfather of this site) but there wasn't a very good cal-hypo puck option at that time. This idea is based on theory, I don't know of any attempts being made on this forum (on the old PoolForum perhaps), and I guarantee nobody has tried with NST tablets, but if a SLAM causes staining then it seems like it could be worth a shot.

 

[JoyfulNoise]

Can you be more specific about the pool? Volume? Chemistries used? Equipment? Fill water chemistry?

There is no easy answer here. The easiest solution will probably involve some level of draining the pool and trucking in metal free water. Then the evaporation from the pool will need to be controlled as well as the metal levels from the fill water. One could try to purposefully precipitate metals using calcium hypochlorite and pillow stuffing, but it's tricky at best and the results are not guaranteed.

Green sand is only used in household water applications. There's no way you'd reasonable construct a green sand filter in a cost effective manner that can treat the volume of water you are talking about in a standard residential pool.

 

[zea3]

Does this customer have a source of iron free water? If it was only being topped off with well water last summer, what did he use to top it off before?

What works with small intex style pools is to fill the pool, slam it to precipitate all the iron and use homemade filters to catch all the iron precipitate. It takes several days with regular monitoring to filter out all the precipitate. You can look up DIY pool filters for iron on youtube to see how it is done.

The best way is to drain and replace with iron free water.

 

[Swampwoman]

+1 on drain and truck water.
But an initial cheaper experiment/solution is to floc the water with alum, specifically Leslies pure alum floc. Control experiment and ph closely...and only attempt in a pool that can vac to waste, preferably with sand filter. Maybe try in test pail first.

Dpending on size of pool, experiment will cost about $50 versus $900 or more for equivalent water trucking.

Watch that ph (keep low) and don't use sequestrant prior to trying treatment. Btw, this is kinda the standard European approach. And water treatment plants in North America. But results seem to be hit or miss in North American residential pools and I believe its due to use of stain and scale products

Hope that helps give you fodder for thought.

Ps what is iron ppm in well and is there a soft water source avail for top ups?
Green sand IMHO will not handle that volume without burning out the resin unless you use a whole house iron curtain dual or quad system which will run up to three times the cost of trucked water

 

[JoyfulNoise]

+1 to floc test!

Thanks SW I forgot about that.

I would suggest either the pure alum floc or, if you can find it, poly-aluminum chloride (PAC) floc. PAC is a little more forgiving in the pH requirements and only leaves behind chloride as opposed to sulfate.


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[TreeFiter]

Can you be more specific about the pool? Volume? Chemistries used? Equipment? Fill water chemistry?

There is no easy answer here. The easiest solution will probably involve some level of draining the pool and trucking in metal free water. Then the evaporation from the pool will need to be controlled as well as the metal levels from the fill water. One could try to purposefully precipitate metals using calcium hypochlorite and pillow stuffing, but it's tricky at best and the results are not guaranteed.

Green sand is only used in household water applications. There's no way you'd reasonable construct a green sand filter in a cost effective manner that can treat the volume of water you are talking about in a standard residential pool.

The pool is an inground vinyl liner pool with a SWG. Roughly 28,000 gallons. Typically in my area, pools have water trucked in from old underground limestone mines. The water is usually pretty good with the exception of high Total Alkalinity.

I try to keep the chemistry more or less in line with TFP practices.

Where the iron came from is a bit of a mystery. The customer is aware of iron in his well water, and has avoided using it to fill the pool in the past, but a past pool guy thought it would be fine to use it, and ever since he has had problems with staining. I don't know how much was added, or exactly how much iron is in the well water, but it is a reasonable assumption that it contributed.

This customer has been realistic about the situation, and has his eye on the big picture. He realizes that it would be worth spending a big chunk of money to fix the problem once, rather than to continue to spend small amounts over and over again to try to control the situation. The pool is part of a vacation rental, so there is a potential to lose money if the staining comes back while guests are there, or if the pool turns green. A truckload of water is roughly $400 for 6000 gallons. So we would be looking at $800 to replace half the water plus the cost of rebalancing and my services.

My thoughts with a greensand filter are that for less than $1000 we could put a system on the pool for a few days to get rid of the iron, and we would be left with the equipment to treat the pool again in the future. I just don't know how much iron a greensand filter can remove, or how much water would be wasted for backwashing the greensand filter. It has the potential to get expensive, but when we account for the lost rental income and the recurring expenses associated with fighting the iron staining, it could be worth it.

- - - Updated - - -

+1 on drain and truck water.
But an initial cheaper experiment/solution is to floc the water with alum, specifically Leslies pure alum floc. Control experiment and ph closely...and only attempt in a pool that can vac to waste, preferably with sand filter. Maybe try in test pail first.

Dpending on size of pool, experiment will cost about $50 versus $900 or more for equivalent water trucking.

Watch that ph (keep low) and don't use sequestrant prior to trying treatment. Btw, this is kinda the standard European approach. And water treatment plants in North America. But results seem to be hit or miss in North American residential pools and I believe its due to use of stain and scale products

Hope that helps give you fodder for thought.

Ps what is iron ppm in well and is there a soft water source avail for top ups?
Green sand IMHO will not handle that volume without burning out the resin unless you use a whole house iron curtain dual or quad system which will run up to three times the cost of trucked water

I'll have to look into the option to floc this pool. I'm not sure I fully understand how this process works. My understanding of flocculants is that they cause particulates to clump and settle out of suspension. How would this eliminate dissolved iron?

 

[Swampwoman]

Alum specifically will bind iron in ideal conditions. So you floc, let it settle to floor for a day, vac to waste.