Iron discoloration and build up in DE filter grids

[rioesmarex]

I have a large pool in Mexico ( 39,000 galls ) that is filled with well water and we have extremely high water temperature for 8 months of the year ( up to 94 degreess F in mid summer )
In addition to my DE filter ( 36 sq.ft.) I also run the incoming water from the well through a series of external filters when I initially fill the pool and when I add water after backwashing or waste out.
The well water is hard and contains sulhur and ( I think ) iron.
The first external filter consists of layered media to filter out the impurities and then the water goes through a second filter
( water softener granules ) to soften the water.
Here's the problem ........ I use tri-chlor tabs ( multi function ) in a floater plus an occasional tab in the skimmer to disolve faster aand I shock periodically but although my chlorine levels are fine, the Ph is always high... 7.9 to 8.0.
Second part of the problem is that my DE filter goes to high pressure within 12 hours of a new re-charge ( 5 coffee cans ) Backwashing will get the pressure back to normal for about 8 more hours and then after each backwash it takes less and less time before the pressure rises again. I add 1 can of DE after every 5th backwash but within a week the grids have to be removed from the filter and cleaned with a water/muriatic acid solution ( soaked overnight, then hosed off and soaked again for 4 hours and then hosed off again before being put back in the filter )
When I open the filter to clean the grids, they are completely caked with a brown colored mud ( hence my belief tht there is iron in the water ). Althought the grids are clean, they are beginning to feel somewhat brittle and I think trhey have reached the end of their usefull life. When I return to Mexico next month I am taking back a brand new set of grids.

Questions: .... 1) does anyone have any idea why my Ph is always high 2) What is causing the brown colored mud to collect on the grids and also stain the walls of my pool slightly 3) I am trying to find out if anybody makes a metal sequesterant for iron in granular rather than liquid form that I could add to my layered media filter, to catch the iron before it even enters the pool..... I could also add liquid sequesterant in maintenance doses directly to the pool water.

Remember.... the extremely high water temp. probably has a lot to do with it and also after a heavy rain the pool turns green and I have to start from scratch to get it reasonably clean again

All suggestion are appreciated

Dave

 

[duraleigh]

Hi, Dave,

Welcome to the forum. Analysis of the pool water always begins with a complete set of test results. It sounds like you cannot provide that right now but, when you get back, post current results for

pH
FC
CC
TA
CH
CYA

That'll help us get a good picture of where you are (chemistry-wise) and how to adjust your pool water to prevent the issues you are currently having.

 

[rioesmarex]

Can do that when I get back but in the interim what can you tell me about the granular sequesterant idea ?

 

[PaulR]

A sequestrant won't remove the metal from the water; it helps keep it from coming out of solution. That's the opposite of what I think you're asking for, a way to precipitate the iron out before it gets into the pool.

I am far from an expert but I remember 30-40 years ago my dad would run the fill water through a tank full of chlorine, then through a sand tank (not the regular filter), trying to get the iron to bind with the chlorine and precipitate out before it hit the pool. I'm not certain I remember this correctly, we'd want someone more chemically inclined to say if this was a good idea or not.
--paulr

 

[rioesmarex]

A sequestrant won't remove the metal from the water;

it helps keep it from coming out of solution. That's the opposite of what I think you're asking for, a way to precipitate the iron out before it gets into the pool.

I am far from an expert but I remember 30-40 years ago my dad would run the fill water through a tank full of chlorine, then through a sand tank (not the regular filter), trying to get the iron to bind with the chlorine and precipitate out before it hit the pool. I'm not certain I remember this correctly, we'd want someone more chemically inclined to say if this was a good idea or not.
--paulr

You're right about sequesterant keepingh the iron in solutiom but that is when the seq. is in liquid form. That's why I'm trying to find out whether a granular sequesterant would stop and hold the iron from getting into the water first. If it does, then I can remove and clean the pre-pool media filter after the pool is filled

 

[JasonLion]

You could use a green earth filter. That will remove nearly all of the iron from the water before it reaches the pool. They do tend to be a little expensive however.

 

[rioesmarex]

You could use a green earth filter. That will remove nearly all of the iron from the water before it reaches the pool. They do tend to be a little expensive however.

Don't have the space to add another separate filter and with the water trying to go through three filters the presure build up would be so high, it would take days to fill the pool ............. that's why I'm trying o find out if there is a granular form that I could layer into my first media filter'
Still open to ideas or input from anyone else ??

 

[frustratedpoolmom]

To my knowledge there is no granular form.

Your high PH is likely caused by high TA, combined with some source of aeration (attached spa, overflow, waterfall, foutain?).

Keeping the PH in the normal range helps with staining - use a sequesterant and keep the PH at 7.4-7.5. There is an article in Pool School on how to lower TA if that is the culprit.

The brown colored mud could also be dead algae. If the water turns green quickly after a rain, then your water is likely out of balance, possibly high CYA and not enough free chlorine. Do you have your own test kit for your return trip? It would be a good idea.

If your CYA is too high, the FC must be high too, to prevent an outbreak - see the CYA chart. If you expect a lot of rain, increase the FC level before hand or immediately after to deal with the after affects. We had inches and inches of rain a few weeks back and my pool did not turn green. It is not a given, it's entirely preventable if you keep your FC up. Unfortunately with trichlor use that isn't always possible.

 

[rioesmarex]

To my knowledge there is no granular form.

Your high PH is likely caused by high TA, combined with some source of aeration (attached spa, overflow, waterfall, foutain?).

Keeping the PH in the normal range helps with staining - use a sequesterant and keep the PH at 7.4-7.5. There is an article in Pool School on how to lower TA if that is the culprit.

The brown colored mud could also be dead algae. If the water turns green quickly after a rain, then your water is likely out of balance, possibly high CYA and not enough free chlorine. Do you have your own test kit for your return trip? It would be a good idea.

If your CYA is too high, the FC must be high too, to prevent an outbreak - see the CYA chart. If you expect a lot of rain, increase the FC level before hand or immediately after to deal with the after affects. We had inches and inches of rain a few weeks back and my pool did not turn green. It is not a given, it's entirely preventable if you keep your FC up. Unfortunately with trichlor use that isn't always possible.

Thanks for the advice ..... yes I have a test kit already .... usually I just add muriatic acid to try and lower the Ph .... it works right off the bat but after awhile it right back up to 7.8 or 8.0 Someone elsae said that by adding too many excess chemicals all the time, that the water has too much phosohates in it which alsoo be the cause of the brown mud. ??

 

[frustratedpoolmom]

Thanks for the advice ..... yes I have a test kit already .... usually I just add muriatic acid to try and lower the Ph .... it works right off the bat but after awhile it right back up to 7.8 or 8.0 Someone elsae said that by adding too many excess chemicals all the time, that the water has too much phosohates in it which alsoo be the cause of the brown mud. ??

If your TA is high and you have a source of aeration, the PH will jump right back up. A high FC level seen when shocking with bleach or Cal-hypo - a FC over 10- will make the PH read a false high. So never test the PH when your FC is above 10 or while you are undergoing a shock treatment - test the PH before. Are you using any product that contain Baking Soda or Soda Ash that might raise PH/TA? For instance, your "multi-function" trichlor tabs - what are the ingredients? I have seen tablets that contain soda ash but I'm not sure if there are any combined with trichlor. Usually we see low pH/TA from the use of trichlor, because they are so acidic.

New plaster, up to 1 year, will experience rapid PH rise...

If your PH rises annoyingly often, we recommend a TA of 60-70 to stabilize the PH. So when you arrive and test the TA, if it's higher than that, you can follow the instructions in Pool School - How to Lower TA.

Were they trying to sell you phosphate remover when they suggested the phosphates were the cause of the brown mud? Nonsense...

The key to BBB and the method we preach here at TFP is knowledge and proper testing are key. Not putting unneccessary (and usually expensive) pool store chemicals in your pool... most of the items we utilize are available in the grocery store or Wal-mart. (I have successfully maintained my pool for three summers now using nothing but Bleach, Borax and CYA. The Borax and CYA this year - the first two summers, nothing but the Bleach! I have not had to use any other products, and the only times I have shocked my pool are for three extended vacations (9-10-11 days) and to winterize my pool.

We can help you figure this out, just keep reading the different threads in the various topics and eventually this will all sink in, you will be on your way to a trouble-free pool.

 

[rioesmarex]

Thanks for the advice ..... yes I have a test kit already .... usually I just add muriatic acid to try and lower the Ph .... it works right off the bat but after awhile it right back up to 7.8 or 8.0 Someone elsae said that by adding too many excess chemicals all the time, that the water has too much phosohates in it which alsoo be the cause of the brown mud. ??

If your TA is high and you have a source of aeration, the PH will jump right back up. A high FC level seen when shocking with bleach or Cal-hypo - a FC over 10- will make the PH read a false high. So never test the PH when your FC is above 10 or while you are undergoing a shock treatment - test the PH before. Are you using any product that contain Baking Soda or Soda Ash that might raise PH/TA? For instance, your "multi-function" trichlor tabs - what are the ingredients? I have seen tablets that contain soda ash but I'm not sure if there are any combined with trichlor. Usually we see low pH/TA from the use of trichlor, because they are so acidic.

New plaster, up to 1 year, will experience rapid PH rise...

If your PH rises annoyingly often, we recommend a TA of 60-70 to stabilize the PH. So when you arrive and test the TA, if it's higher than that, you can follow the instructions in Pool School - How to Lower TA.

Were they trying to sell you phosphate remover when they suggested the phosphates were the cause of the brown mud? Nonsense...

The key to BBB and the method we preach here at TFP is knowledge and proper testing are key. Not putting unneccessary (and usually expensive) pool store chemicals in your pool... most of the items we utilize are available in the grocery store or Wal-mart. (I have successfully maintained my pool for three summers now using nothing but Bleach, Borax and CYA. The Borax and CYA this year - the first two summers, nothing but the Bleach! I have not had to use any other products, and the only times I have shocked my pool are for three extended vacations (9-10-11 days) and to winterize my pool.

We can help you figure this out, just keep reading the different threads in the various topics and eventually this will all sink in, you will be on your way to a trouble-free pool.

Thanks for the extra advice... will keep it all in mind and re- analyse when I get back to my pool. Have pretty much decided to go with standard stabilized tr-chlor 99% tabd and to shock with 73% hypo shock or 13% pure liquid chlorine and stay away from multi function tabs / chemicals

 

[polyvue]

Have pretty much decided to go with standard stabilized tr-chlor 99% tabd and to shock with 73% hypo shock or 13% pure liquid chlorine

Hello rioesmarex,
I didn't see any test result numbers posted so I would urge you to obtain a good test kit (TF-100 and Taylor K-2006 are both quite useful - take your pick) and evaluate your test results before deciding a particular route of pool treatment. You can do it the other way around, but you may find yourself back here with pool water that you have to "un-do"

For example, you mentioned that you've decided to use TriChlor to chlorinate your pool. That may be OK, but you don't want to start using TriChlor until you know your CYA level (since TriChlor adds a considerable amount of CYA along with the chlorine); the outcome could be a pool with high levels of both chlorine and CYA that is both unsanitary and susceptible to algae.

 

[rioesmarex]

Have pretty much decided to go with standard stabilized tr-chlor 99% tabd and to shock with 73% hypo shock or 13% pure liquid chlorine

Hello rioesmarex,
I didn't see any test result numbers posted so I would urge you to obtain a good test kit (TF-100 and Taylor K-2006 are both quite useful - take your pick) and evaluate your test results before deciding a particular route of pool treatment. You can do it the other way around, but you may find yourself back here with pool water that you have to "un-do"

For example, you mentioned that you've decided to use TriChlor to chlorinate your pool. That may be OK, but you don't want to start using TriChlor until you know your CYA level (since TriChlor adds a considerable amount of CYA along with the chlorine); the outcome could be a pool with high levels of both chlorine and CYA that is both unsanitary and susceptible to algae.

Thanks for the comment ..... everything is helpful. When I said I had decided to go with straight Tr-Chlor tabs, what I meant was, straight vs. the multi function kind. If the Tri-Chlor tabs add CYA, then what are other options for basic daily chlorination/sanitation of the pool are there ? I have access to straight high strength liquid chlorine ( 13% ) ( no additives ) which is definitely cheaper than the tabs but it is inconvenient to use .... ( no way to place into the water automatically ... like wiith a tab auto chlorinator ) .... it is bulky ... 30 gallon plastic cask ...... and I have used it in the past and it didn't really seem to cure the problem and the FC levels in the pool did not stay up due to burn-off ( no stabilizer in liquid chlorine ) and the Ph levels were still high. So gave up and bit the bullett cost wise and started to use the tabs ..... but as you can tell from the thread, still no luck. I don't know of a liguid chlorine automatic dispenser but if there were one, I imagine it would be very bulky and be very expensive. ( All my equipment is in a pit with a lid on it and I have virtually no more space to add annything ) I have purchased an off-line tablet chlorinator that I planned to use with the tri-chlor tabs ???
Any more thoughts or conclusions ?
My biggest problem is once I get back to Mexico I have a very limited ( and expensive ) source of equipment supply so I try to buy everything I need when I come up to the U.S. for my annual visit to the grand-kids. Also there is a very limited source of good water testing facilities near me and it takes me a week to return to Florida by road so bringing water samples with me doesn't really work.
I did bring a sample once and it tested fairly good other than showing small traces of iron and also being very hard water. The guy reading the test results said there were also small trace of tannin .... but then in Florida anything brown is tannin and I doubt he was right cause nobody in my part of Mexico has ever even heard of tannin.. I bought a special set of pre-pool filters to pre-filter my well water befor it inters the pool and goes through the Haywrd DE filter. The first is layered media to remove the traces of contaminants indicated from the water test and the second is a straght water softener media ....
( granular ) to take care of the hard water .... that part works... the water is soft now untilt it gets contaminated by rain water. Also to clarify things a little more we live within a mile from a salt/fresh water estuary and the water table is very high ( about 20 ft ) so I don't know whether that has any effect on the ground water. The well is 60 ft deep.

Dave

 

[polyvue]

If the Tri-Chlor tabs add CYA, then what are other options for basic daily chlorination/sanitation of the pool are there ? I have access to straight high strength liquid chlorine ( 13% ) ( no additives ) which is definitely cheaper than the tabs but it is inconvenient to use .... ( no way to place into the water automatically ... like wiith a tab auto chlorinator ) .... it is bulky ... 30 gallon plastic cask ...... and I have used it in the past and it didn't really seem to cure the problem and the FC levels in the pool did not stay up due to burn-off ( no stabilizer in liquid chlorine ) and the Ph levels were still high.

I understand the attraction, even the necessity, of having a convenient method of adding chlorine to the pool. You could install a Salt Water Generator (SWG) on the pool that would address this concern. The principal cost is the initial purchase ($700-$1500) but after installation, your only significant cost is a few bags of salt each year. And it would keep your pool chlorinated while you travel.

Another option: Use the Trichlor puck feeder only when you travel; when in Mexico, add chlorine (from your bulk container or gallon jugs) as needed. Either way, you will have to conduct testing at least once a week to make sure Free Chlorine (FC) and cyanuric acid (CYA) levels are OK.

The only other alternative would be employing a pool service... but you may have to teach them how to test your water and tell them when to add chlorine, etc. Don't leave it up to them.

[T]here is a very limited source of good water testing facilities near me and it takes me a week to return to Florida by road so bringing water samples with me doesn't really work

Pool water is not meant to be transported before it's tested. Buy a test kit and leave it in Mexico near your pool.

 

[chem geek]

In addition to the excellent suggestions already made, there is another option for being able to add chlorine once a week to the pool. One can have the CYA level be high, especially in very sunny hot areas, up to 100 ppm. One then raises the FC level to around 14 ppm and by the next week the FC usually drops to around 4 ppm at which point one adds 10 ppm to get the FC back up to 14 ppm. The only real downside to this approach is that the chlorine level swings a lot, but that's going to happen with any once-a-week chlorine addition method. One also has to be careful to not miss a dose since fighting an algae outbreak at such a high CYA level is far harder to do. One can use 50 ppm Borates to supplement the process and provide some mild algae inhibition [EDIT] and some additional pH buffering lessening the swing in pH from the large weekly chlorine addition [END-EDIT], but it is the chlorine itself that does most of the work preventing algae. If you had regular water dilution, then you could supplement with a small amount of Trichlor, but not too much or the CYA will build up.

As was noted by others, the well water is probably very high in TA and that is the cause of the pH rise, along with aeration. It's a pay-me-now vs. pay-me-later situation where you can lower the TA with a lot of acid up-front or you can lower it over time via much more frequent acid addition over time. If the pH was rising in spite of using Trichlor tabs, then the TA must be extraordinarily high and/or there is lots of aeration.

Evaporation and refill will add to the pool water whatever is in the fill water. If you get a pool cover for the pool, it should significantly cut down the rate of pH rise and the buildup of TA and CH and other items (e.g. metals) from the fill water. Of course, covering the pool will tend to make it too hot so a white or reflecting opaque and not particularly insulating (i.e. thin) cover would probably be better in your situation and you may find that it keeps the pool somewhat cooler by preventing the water from getting heated up by the sun during the day (on the other hand, it also prevents it from getting cooled down at night -- the water should roughly approach the average day/night air temperature).

Richard

 

[rioesmarex]

In addition to the excellent suggestions already made, there is another option for being able to add chlorine once a week to the pool. One can have the CYA level be high, especially in very sunny hot areas, up to 100 ppm. One then raises the FC level to around 14 ppm and by the next week the FC usually drops to around 4 ppm at which point one adds 10 ppm to get the FC back up to 14 ppm. The only real downside to this approach is that the chlorine level swings a lot, but that's going to happen with any once-a-week chlorine addition method. One also has to be careful to not miss a dose since fighting an algae outbreak at such a high CYA level is far harder to do. One can use 50 ppm Borates to supplement the process and provide some mild algae inhibition, but it is the chlorine itself that does most of the work preventing algae. If you had regular water dilution, then you could supplement with a small amount of Trichlor, but not too much or the CYA will build up.

As was noted by others, the well water is probably very high in TA and that is the cause of the pH rise, along with aeration. It's a pay-me-now vs. pay-me-later situation where you can lower the TA with a lot of acid up-front or you can lower it over time via much more frequent acid addition over time. If the pH was rising in spite of using Trichlor tabs, then the TA must be extraordinarily high and/or there is lots of aeration.

Evaporation and refill will add to the pool water whatever is in the fill water. If you get a pool cover for the pool, it should significantly cut down the rate of pH rise and the buildup of TA and CH and other items (e.g. metals) from the fill water. Of course, covering the pool will tend to make it too hot so a white or reflecting opaque and not particularly insulating (i.e. thin) cover would probably be better in your situation and you may find that it keeps the pool somewhat cooler by preventing the water from getting heated up by the sun during the day (on the other hand, it also prevents it from getting cooled down at night -- the water should roughly approach the average day/night air temperature).

Richard

More good info and I making a list of all the comments to come up with an average best solution.
Funny co-incidence Richard .... I also live in San Rafael .... but this is SanRafael in Veracruz sate of mexico

 

[rioesmarex]

If the Tri-Chlor tabs add CYA, then what are other options for basic daily chlorination/sanitation of the pool are there ? I have access to straight high strength liquid chlorine ( 13% ) ( no additives ) which is definitely cheaper than the tabs but it is inconvenient to use .... ( no way to place into the water automatically ... like wiith a tab auto chlorinator ) .... it is bulky ... 30 gallon plastic cask ...... and I have used it in the past and it didn't really seem to cure the problem and the FC levels in the pool did not stay up due to burn-off ( no stabilizer in liquid chlorine ) and the Ph levels were still high.

I understand the attraction, even the necessity, of having a convenient method of adding chlorine to the pool. You could install a Salt Water Generator (SWG) on the pool that would address this concern. The principal cost is the initial purchase ($700-$1500) but after installation, your only significant cost is a few bags of salt each year. And it would keep your pool chlorinated while you travel.

Another option: Use the Trichlor puck feeder only when you travel; when in Mexico, add chlorine (from your bulk container or gallon jugs) as needed. Either way, you will have to conduct testing at least once a week to make sure Free Chlorine (FC) and cyanuric acid (CYA) levels are OK.

I alreaady had a SWG and it was total disaster and in my case a waste of money. It was supposed to be rated at 40,000 gallons but it could not produce anywhere near enough chlorine. I went around and around with the manufacturer Aqua Rite who were totally unconcerned and could offer no usefull fixes. The end result was, ... the cell was bad but because I had installed it in Mexico rather than the U.S. they refused to honow the guarantee .... so I won't deal with those a.s h...s again

The only other alternative would be employing a pool service... but you may have to teach them how to test your water and tell them when to add chlorine, etc. Don't leave it up to them.

Yeah ... wink is right. The guys sweping the pool would fall asleep and fall iin the pool if the brush wasn't holding himm up

[T]here is a very limited source of good water testing facilities near me and it takes me a week to return to Florida by road so bringing water samples with me doesn't really work

Pool water is not meant to be transported before it's tested. Buy a test kit and leave it in Mexico near your pool.

I have several test kits and use them every day but they don't test for iron or phosphates or tannin and as mentioned earlier there are no facilties near me for a full reliablew water analysis

 

[frustratedpoolmom]

IF you search the forum for "The Liquidator" you can see that automated dosing method for liquid chlorine.

I second the suggestion for an SWG....

I alreaady had a SWG and it was total disaster and in my case a waste of money. It was supposed to be rated at 40,000 gallons but it could not produce anywhere near enough chlorine. I went around and around with the manufacturer Aqua Rite who were totally unconcerned and could offer no usefull fixes. The end result was, ... the cell was bad but because I had installed it in Mexico rather than the U.S. they refused to honow the guarantee .... so I won't deal with those a.s h...s again

Perhaps you don't want to go down that road again, but there may have been specific reasons why there were problems, water chemistry issues, etc., that caused it to not work out for you.

If you were trying to use chlorine before without any CYA in the water, that would explain the rapid burn-off. If you maintain proper CYA levels - you would only need to add a small amount of chlorine each nite, or every other nite, to stay above the recommended minimum level.

If your pool is consuming more than 2ppm daily, there could have been a nascent algae situation consuming the FC levels rapidly.

If you want to use the trichlor, that's fine, just monitor your PH and TA and keep the CYA below 50ppm or you will likely not be able to maintain the FC at the proper level to prevent algae. Perhaps a combination and supplementing with some liquid too will work for you.

 

[polyvue]

Perhaps you don't want to go down that road again, but there may have been specific reasons why there were problems, water chemistry issues, etc., that caused it to not work out for you.

If you were trying to use chlorine before without any CYA in the water, that would explain the rapid burn-off. If you maintain proper CYA levels - you would only need to add a small amount of chlorine each nite, or every other nite, to stay above the recommended minimum level.

Yes, this could explain why the SWG didn't work as you had hoped.

The only other alternative would be employing a pool service... but you may have to teach them how to test your water and tell them when to add chlorine, etc. Don't leave it up to them.

Yeah ... wink is right. The guys sweping the pool would fall asleep and fall iin the pool if the brush wasn't holding himm up

Funny! :lol: Even if you employed a service that sent out a hard worker who required no supervision, they might still not have sufficient knowledge of pool chemistry.

 

[rioesmarex]

Perhaps you don't want to go down that road again, but there may have been specific reasons why there were problems, water chemistry issues, etc., that caused it to not work out for you.

If you were trying to use chlorine before without any CYA in the water, that would explain the rapid burn-off. If you maintain proper CYA levels - you would only need to add a small amount of chlorine each nite, or every other nite, to stay above the recommended minimum level.

Yes, this could explain why the SWG didn't work as you had hoped.

The only other alternative would be employing a pool service... but you may have to teach them how to test your water and tell them when to add chlorine, etc. Don't leave it up to them.

Yeah ... wink is right. The guys sweping the pool would fall asleep and fall iin the pool if the brush wasn't holding himm up

Funny! :lol: Even if you employed a service that sent out a hard worker who required no supervision, they might still not have sufficient knowledge of pool chemistry.

Glad you had a laugh at that !!

Anyway, does anyone know where I could buy a product called " The Liquidator " made by Hasa to dispense liquid chlorine into the pool automatically. What would be the normal price for this product ( the biggest one ,,,, 8 galllon, I think ) or what would be a real good price from who ? on-line