Can a sand filter appear to be working but actually not?

[mcgeggy]

I have an old Doughboy sand filter that I inherited when I bought my house in 2002, for a 24' round AGP. Since that time I've replaced both the pump and the entire pool. The filter seems to be operational, I changed out the sand last summer, all of the valve settings do what they are supposed to do.

I just replaced the liner, used my well water to fill, and have been struggling for the last week with emerald green, but clear water. Added seven bottles of metal out (varying brands), both before chlorinating and after, and the water does not seem to care one bit. Every time I backwash, the water coming out is clear. It's like nothing is being filtered. But the pressure out of the return is good, no leaks, no sand into pool. But still, debating weather I should just go ahead and replace it anyway. Or is it the type of thing where you know the filter is a goner because there is a leak, or one of the valve settings doesn't do what is supposed to, etc?

I didn't have so much trouble 7 years ago getting the green water to turn to blue/clear when I replaced the pool. Getting desperate to figure out why it's being so stubborn this time...

 

[Catanzaro]

Please be specific on exactly what the issue is. In addition, why did you use well water? I live in the area and driving around seeing sidewalks all full or rust reminds me that well water is not a wise choice. To fill my pool, I spent $100 on water and skipped the well water (have both). If your water is green, the well water probably is the culprit.

 

[tphaggerty]

You might want to check that the hoses to the filter are attached correctly. My neighbor hooked theirs up backward last year and although everything seemed to work, it definitely was not filtering. In their case, the backflush was really weak as well. There are a number of threads here on TFP about this problem, that’s how I found the answer!

 

[mcgeggy]

Please be specific on exactly what the issue is. In addition, why did you use well water? I live in the area and driving around seeing sidewalks all full or rust reminds me that well water is not a wise choice. To fill my pool, I spent $100 on water and skipped the well water (have both). If your water is green, the well water probably is the culprit.

I already know the well water is the culprit. Delivered water is way more $ than $100 in my area. I’ve used my well water in the past to fill, and metal out product got rid of the green color, permanently. All of the “top offs” with well water over the next 7 years never turned it green again. But this time nothing seems to be working. Obviously I was not anticipating this result.

So I wonder if my very old sand filter is somehow not filtering. That’s what I was asking. In the past the process was add metal out, run filter 24 hours. Each 24 hour period the water would get clearer. Took 3-4 days and bottles, but water clear at end. Not this time. Bad filter?

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You might want to check that the hoses to the filter are attached correctly. My neighbor hooked theirs up backward last year and although everything seemed to work, it definitely was not filtering. In their case, the backflush was really weak as well. There are a number of threads here on TFP about this problem, that’s how I found the answer!

Thanks, but yeah I double checked that first. Just wondering if somehow the water inside the filter could be bypassing the sand somehow... This filter may be 20-30 years old by now!

 

[zea3]

The filter won't remove the green tint from the water. That is what the sequestrant does. Which sequestrant are you using? What is the pressure reading on the filter when the pump is running? Also please post a current set of test results.

 

[mcgeggy]

The filter won't remove the green tint from the water. That is what the sequestrant does. Which sequestrant are you using? What is the pressure reading on the filter when the pump is running? Also please post a current set of test results.

The pressure gauge is not working. I've used Pro Team Metal Magic (old leftover unopened bottle), a new bottle of Natural Chemistry Metal Free, Ultimate Backyard Products Metal Control, and hth Metal and Stain Defense. The first two products were added before chlorinating and no change in 36-48 hours. pH was 7.2. Then I shocked, but did not add any CYA. No change. Added clarifier, no change. Shocked using several gallons of chlorine, hoping to oxidize the metal and get it out by vac after floc. Filter running non-stop for a week now. Every morning I look out hoping to see an improvement and there is none. I don't know why it was so much easier the last times I filled with well water. I've also tried using the DIY poly fill bucket filter. The poly fill was clean white after 24 hours. I left a wad of it in the skimmer basket, but it stays white.

 

[zea3]

I'm going to ask a bunch of different questions to try and troubleshoot your problem. FYI, I'm not trying to be snarky, just looking for a clue to follow. Are you using any one particular brand of chlorine? Does the chlorine you use say anything on the label like Chloromax technology, or special fabric protectors, or keeps fabrics white longer? When you backwash does the pressure gauge register anything? What are your current test results, and how often are you adding chlorine?

 

[Catanzaro]

The gauge is not working. Please purchase a quality gauge. TFTestkits.net offers gauges. In addition, it is very possible the your well water contains more metals than prior. And your sand filter is designed to keep the water clean, not remove metals.

 

[mcgeggy]

I'm going to ask a bunch of different questions to try and troubleshoot your problem. FYI, I'm not trying to be snarky, just looking for a clue to follow. Are you using any one particular brand of chlorine? Does the chlorine you use say anything on the label like Chloromax technology, or special fabric protectors, or keeps fabrics white longer? When you backwash does the pressure gauge register anything? What are your current test results, and how often are you adding chlorine?

OK, thanks!

Chlorine:
-Pool Essentials Chlorinating Liquid (Walmart, gallon jugs)
-genric supermarket bleach (no additives)

Current test results (as of 10 minutes ago):
TA 60
pH 7.4
FC 3
CC 1.5
TC 4.5
did not test for CYA because I have not added any.

As for how often I add chlorine? I added about 2 gallons two days ago in late afternoon. I am conflicted about the chlorine situation - most of the metal out products (and searches on this forum) advise using the product before adding chlorine, or when chlorine is low or 0. On the other hand, I have also come across info about high chlorine causing metals to oxidize, and then they should be easier to remove through filtering or vacuuming. I don't want to keep the chlorine low and continue to spend $ on metal out products that don't seem to be doing anything. So I add chlorine so at least me daughter and I can swim. But if someone recommends a metal out product and/or procedure to use it, I don't want to struggle to get the chlorine low because I added CYA.

I replaced this liner due to a slow leak for the past 5 years, and the fact that the blue in the liner became very faded, and I didn't like how it looked through my (previously) clear water. I was really looking forward to the new liner color and how the pool water would appear. But so far all I have is that weird emerald green...

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The gauge is not working. Please purchase a quality gauge. TFTestkits.net offers gauges. In addition, it is very possible the your well water contains more metals than prior. And your sand filter is designed to keep the water clean, not remove metals.

At this point I am still deciding if I should just spend the $200 on a new filter, maybe the Hayward S166T ProSeries Sand Filter, 16-Inch, Top-Mount (Amazon). Replacing parts on the old Doughboy can be very expensive. I'm sure seals and brittle plastic pieces will continue to need replacement.

The DIY poly fill in a bucket filter is supposed to work, and it has not seemed to do anything either, at least judging by the pure white color of the material...

 

[Swampwoman]

Hi there.
The metal out products you used have different components...not sure this would make any difference but stick to metal magic...way more reliable than natural chemistry.

Can you post a pic? It’s not entirely surprising that your polyfill isn’t discoloring considering you’ve added the Sequestrant, but weird that you still have the tint.

On one hand, sequestrant demand varies in proportion to the amount of metals so you can and clearly may need more than you’ve used(and of the same product). But filtration does play a role so I too would be a bit suspicious. When you backwash, is the water in the site glass milky at all?

Why not get your metals tested at the pool store (the only time we’re C.C. using the pool store ) so we know what we’re dealing with. If there was any copper exposure, then a partial drain may be in order despite the iron in well.

Btw, how much iron is in your well water?

 

[mcgeggy]

Hi there.
The metal out products you used have different components...not sure this would make any difference but stick to metal magic...way more reliable than natural chemistry.

Can you post a pic? It’s not entirely surprising that your polyfill isn’t discoloring considering you’ve added the Sequestrant, but weird that you still have the tint.

On one hand, sequestrant demand varies in proportion to the amount of metals so you can and clearly may need more than you’ve used(and of the same product). But filtration does play a role so I too would be a bit suspicious. When you backwash, is the water in the site glass milky at all?

Why not get your metals tested at the pool store (the only time we’re C.C. using the pool store ) so we know what we’re dealing with. If there was any copper exposure, then a partial drain may be in order despite the iron in well.

Btw, how much iron is in your well water?

Hi, thanks for responding! My filter is so old, it doesn't have a sight glass. The backwash never changes color. I'm getting desperate so I fear if I go to pool store for testing they will convince me to walk out with more expensive chemicals that may or may not work, lol. I had an iron test strip leftover from a water testing kit, and the iron was not really high at all, but I used it on the pool water not straight from the well.

So I added floc two nights ago, and while it did not seem to leave anything sitting on the pool bottom the next morning (after leaving pump off overnight), the water did seem to be slightly less green. But then it was back to the previous shade by early evening, filter running the whole time. But the wad of polyfill I left in the skimmer basket did seem to be rust colored! I replaced it last night, and hooked up the polyfill bucket filter too. But then I added more floc last night, left pump off, and this morning the water was cloudier, but looking bluer.

I'm going to open the polyfill bucket and change out the fill. The skimmer wad is rusty colored again. I added more chlorine as well as the pucks in the floater. The problem with the polyfill bucket is that it does not circulate the pool water like the return does.

I ordered a new filter, the one I mentioned above. It's possible that the sand in the filter is corrupt somehow. I don't want to open it and check, as I will need to replace the big o-ring, and buy a new gauge, and any other parts or pieces that may break, so I said I'll just buy a new filter. Looking at using glass media, or Dr. Dryden's Activate, as it supposed to be better at filtering iron.

Also, for the past 4-5 years I'd been using Robelle 3 month algaecide (copper based) and never had any issue with algae, metal stains, blonde hair turning green, etc. All the top offs with well water did not change the color at all. I don't know why it is so hard this time. What a PITA! Oh, and I got a quote to deliver 13,600 gallons of pool water: $1100. No thanks!

 

[mcgeggy]

Well, something seems to have finally clicked! The pool is looking blue finally (a bit cloudy, but blue!) The polyfill in the skimmer basket was saturated with rusty brown color, and rusty brown water finally came out of the backwash for a few minutes. I still have to open up the DIY polyfill bucket, but I'm sure I will find it nice and dirty. I've taken it offline for now to get some decent circulation into the pool via the return. Hopefully I have turned a corner.