Help - major algae now cloudy pool

[14me2]

When did you change your sand last? If everything else looks good, this could be the culprit.

[duraleigh]

When did you change your sand last? If everything else looks good, this could be the culprit.

Hi, 14me2,

Hmmmm, this "change the sand" issue has me puzzled.

Matt4x4 and others here are advocates of doing so, but I've never understood the logic. In fact, many of us think "old" Sand may filter even better than new. (I'm not so sure about that one but it's logic has some merit)

I think Xioronix's issue is with dead algae. If he'll keep filtering and keep his Cl levels up, I think he'll have clear water. (Actually, his other issue would be to change that username to something I could spell!! )

Dave S.

[CarlD]

Changing your sand is only appropriate if:
1) It's all gummed up from the other chemicals you added. If so, then, yes, change it.
2) if the algae bloom is deep into the sand itself, the only good solution may be to replace the sand--I gather it can be hard to kill if the sand itself is badly infested.

Otherwise, simply follow the standard algae-clearing plan:
1) keep FC at the recommended shock level for your CYA level. Use bleach or liquid chlorine, only. Keep pH in the 7.3-7.8 range, but try for the lower end (7.3-7.5).
2) Test FC 3x/day and adjust to keep it up.
3) Brush the pool every day to keep algae from bedding into the floor and walls
4) Run your filter 24/7. Clean/backwash everytime the pressure rises.
5) Vacuum TO WASTE everyday.
6) Don't add lots of pool-store junk in hopes of a quick-fix--ain't gonna happen.
7) Have lots and lots of patience and persistence. You are in for a week to 2 weeks of work. Be consistent and it will clear faster
8) AFTER your water is clear, you can add PolyQuat 60% to help keep it from happening again.

[aylad]

[/QUOTE]AFTER your water is clear, you can add PolyQuat 60% to help keep it from happening again.[/QUOTE]

That, and make sure your chlorine levels stay up!!

Janet

[waterbear]

Hmmmm, this "change the sand" issue has me puzzled.

Matt4x4 and others here are advocates of doing so, but I've never understood the logic. In fact, many of us think "old" Sand may filter even better than new. (I'm not so sure about that one but it's logic has some merit)


Dave S.

This issue I wonder about. Have never used a sand filter in a pool but have used sand as a mechanical filter medium in large aquariums. General concensus there is that the constant flowing of the water over the sand erodes the facets off the silica crystals and rounds and polishes them. It is believed that this leads to channeling and increases the minimum particle size that can be filtered by the medium making it less effecient. Don't know if the same factors will apply in a pool filter but I suspect they might. Anyone have some info either way? I am curious about the logic of not changing the sand. Why do you think old sand may filter better than new? (by the way, this info is not "fish stored"
because there are very few commercial sand filters for aquarums and most aquarists build their own)

[duraleigh]

Hi, bear,

Yeah, the issue is interesting to me, too. Let me say, first of all, that I've got a big sand filter and my water is pristine....I couldn't imagine it could be improved.....naturally, it follows I am a big advocate of sand.

I'm not sure I agree with this but the thinking of others on the forum is that, as the sand captures smaller particles, it captures smaller and smaller particles as they accumulate. If so, then it would seem backwashing would eliminate any temporary advantage.

Your thought of the "rounding off" of the sand particle might likewise have some merit. However, might not the rounded particles "fit" tighter together allowing them to capture smaller particles?

My thinking about channeling is that it's caused by the filter being undersized causing the water to pass through the filter at an excessive velocity.

So, since I can't come to a logical conclusion that changing the sand will provide a benefit I can see or understand, I plan on leaving mine in there.

I have no idea if my thought process is correct or if any of this matters a hill of beans to anyone but it's too dark to go outside and mess with the pool and there's never anything decent on TV.

Dave S.

[waterbear]

Hi, bear,

Yeah, the issue is interesting to me, too. Let me say, first of all, that I've got a big sand filter and my water is pristine....I couldn't imagine it could be improved.....naturally, it follows I am a big advocate of sand.

I'm not sure I agree with this but the thinking of others on the forum is that, as the sand captures smaller particles, it captures smaller and smaller particles as they accumulate. If so, then it would seem backwashing would eliminate any temporary advantage.
But if your backpressure is too high you will not get effecient water flow through the medium so cleaning the filter medium is essential.
And it is well known among aquarists that a freshly cleaned mechanical filter medium does not filter as effeciently as one that has been in service for a while.
Your thought of the "rounding off" of the sand particle might likewise have some merit. However, might not the rounded particles "fit" tighter together allowing them to capture smaller particles?
From my understaning it is the sharp edges on the sand grains that provide the mechanical filtration. The particles get caught up in the junctures between the sand grains. Once they 'round off" there is less places for them to get caught and the sand grains act like tiny ball bearings. It is true that as a filter becomes slightly dirty it will tend to filter better becuase the spaces between the grains (or pores in the cartridge matierial in a cartridge filter) become smaller due to the trapped particles. The reason many add a bit of DE to both sand and cartridge filters, in fact.

My thinking about channeling is that it's caused by the filter being undersized causing the water to pass through the filter at an excessive velocity.
My take on it is the rounded grains provide less resistance to the force of the water, having fewer edges and sides to deflect the water in different directions. This allows the water to pass through the medium at a faster rate which can then lead to channeling. I have actually observed this in a slow sand bed filter that I built for an aquarium. I actually got a faster flow rate through the filter after it had been in use for 3 years with the same sand.
So, since I can't come to a logical conclusion that changing the sand will provide a benefit I can see or understand, I plan on leaving mine in there.

I have no idea if my thought process is correct or if any of this matters a hill of beans to anyone but it's too dark to go outside and mess with the pool and there's never anything decent on TV.

Dave S.

I wonder if any acutal studies have been done on this. Like I said, my experience with sand is using it in large aquarium filters (both pressurized like a pool filter and in open configurations usually called an "under over" or "slow sand bed filter") and nuch of what I learned was from belonging to aquarium clubs and reading books on the subject.
I guess the jury is still out on this one!

[14me2]

To an extent, old sand is good, but take it from experience... I have wasted a lot of time and money trying to let it filter itself, as my parents never changed their sand that Iknow of. I know this is probably untrue, but we have had our pool for 5 years. We used the same sand forever, then all of a sudden we couldn't get the pool to clear. It was a beautiful color, but not sprakling clear... we tried everything, finally we changed the sand. Clear in 2 days!! Fast forward to last year, We had not opened the pool the previous summer... due to a sickness. We had everything right, but the water was grey. We tried floc, and drop out and super blue and tons fo others miracle things, but the cheapest and fastest of them all was jsut some good ol fashioned sand. It looked better over night. And the price of that sand was jsut a bit more than the bottle of drop out. So, I mean what's the worst thing that could happen.

ETA: After a while there will be little channels of sand in your filter, this is not doing anything to filter, (it looks like ants live in there) but allowing it to make it right back into the pool. If you treat your sand at the beginning and end of season, then yes your sand will last longer, but most people don't and relaly it is just as easy to go ahead and change it yearly. Sand will harden and the the water will have to flow somewhere, so it makes the channels....

[ivyleager]

After a while there will be little channels of sand in your filter, this is not doing anything to filter, (it looks like ants live in there) but allowing it to make it right back into the pool. If you treat your sand at the beginning and end of season, then yes your sand will last longer, but most people don't and relaly it is just as easy to go ahead and change it yearly. Sand will harden and the the water will have to flow somewhere, so it makes the channels....

I've used the rinse option for this....stirs up the sand....then resettles in filter option. Do you have this option on your sand filter? This will be my 3rd season w/ pool and I think filter is doing a good job. I did treat sand following 1st season at closing/draining of pipes, but not this year as I kept everything online and cycled pump when temps were below freezing.

CaryB