Floc and sand

[Alaska Mike]

Split from this topic. This side conversation has moved away from the original topic. JasonLion

How often are you backwashing your pool? HTH test strips are not the top of the line. HTH was good company until it got bought and sold a few times. Aquacheck is one we like. We maintain about 600 pool customers and don't have a liquid test kit on the place.

Looks like you just need to floc the pool and vacuum to waste once it settles. Backwash the filter, and don't backwash again until your pressure rises 7-8 pounds above clean pressure.

Could be sand is worn out. It will usually last 5-7 years on chlorine pools. You can test by opening the filter and roll some between thumb and forefinger. If the sand 'flops" it is OK. If it "rolls" it has worn and rounded the corners off and is wore out. Sand is cheap. If you have any doubts, bug some good filter sand and replace it. It has to be filter sand, not the playground sand you buy at Lowe's or Menards.....

 

[JohnT]

Re: I still have a cloudy pool

How often are you backwashing your pool? HTH test strips are not the top of the line. HTH was good company until it got bought and sold a few times. Aquacheck is one we like. We maintain about 600 pool customers and don't have a liquid test kit on the place.

Looks like you just need to floc the pool and vacuum to waste once it settles. Backwash the filter, and don't backwash again until your pressure rises 7-8 pounds above clean pressure.

Could be sand is worn out. It will usually last 5-7 years on chlorine pools. You can test by opening the filter and roll some between thumb and forefinger. If the sand 'flops" it is OK. If it "rolls" it has worn and rounded the corners off and is wore out. Sand is cheap. If you have any doubts, bug some good filter sand and replace it. It has to be filter sand, not the playground sand you buy at Lowe's or Menards.....

Baloney. The sand isn't going to wear out in 5-7 years.

Floc is just a shortcut to good pool care. Filtration and chlorine will clear any pool. Buying unneeded chemicals is no help.

 

[jblizzle]

Re: I still have a cloudy pool

Agree with what John said.

also backwash when the pressure goes up 20-25% of your clean pressure ... The backwash pressure varies for every pool.

Posted with Tapatalk ... sorry if I sound short ... hate typing on phone

 

[Alaska Mike]

Re: I still have a cloudy pool

Removing algae from a pool is a two step process. First you have to kill the algae. The next step is to remove the dead algae from the water. A sand filter will not catch the really fine particles of an algae bloom. That is why you add a clarifier to the water to help those algae particles clump together so the sand filter can catch it. The other option is to floc the pool, turn off the pump, and let the floc carry everything to the bottom. Then vacuum to waste and get rid of the dead algae.

Using a clarifier will take 4 to 5 days. Using a floc will take 24-36 hours. A quart of floc sells for $21.95, a quart of clarifier costs $21.95. Take your choice.

I run a pool store, build and service pools. My most important job is to educate my customers, so they can take control of their pool, save money, and enjoy their pool. I am not going to make any money from someone who reads this website. I do this just to help out, so I think it will be hard for anyone to question my motives here. I get the feeling that some on this site seem to enjoy "bashing" pool stores, and advocate never going back to the store, buying everything they need at the grocery store.

I agree that there are some "bad pool stores", places that like to sell lots of chemicals and keep you running in circles. A good store will help you, and you will help them, by supporting them with your dollars. You just have to find the right store, educate yourself with their help.

The best part about this site, is it advocates checking your pool everyday. That is exactly what I tell my customers. My analogy is a beautiful garden. If you see a beautiful garden, it is not what the owner did yesterday, it is what he or she has been doing for a month. Ten minutes a day is all it takes to maintain a beautiful pool.

Lastly, does sand wear out? Yes, everything wears out. Will a sand filter work with 10 to 20 year old sand? Sure, but will it work as well as new sand, no. You want the best for your pool, you want it to be as easy as possible. Spend $25 to $30 and buy new sand and make your life easier. Remember, there are some people you will meet in life that are prouder of what they paid, rather than what they have. I would rather spend a little money, and have something nice, than brag about how cheap I am.

 

[JasonLion]

Re: I still have a cloudy pool

A sand filter will not catch the really fine particles of an algae bloom.

A sand filter is perfectly capable of clearing up the water without any clarifier or floc. It does take about a week, but it works perfectly well and it doesn't cost anything extra.

Lastly, does sand wear out? Yes, everything wears out.

Certainly in an absolute sense, sand can wear out. However that takes way more than a lifetime. Long before the sand wears detectable the filter it is in will have broken and need to be replaced. So in practice sand lasts as "forever". We have micro-photographs of new and old sand that are indistinguishable, and many many users with ten or twenty year old sand who have perfect sparkling water despite their "old" sand. There really is no detectable difference in the sand after twenty years of use.

Floc can dramatically speed up the process of clearing a pool, but it has a number of problems. First, not everyone has a system that can vacuum to waste. Without that ability, using floc is very problematic. Second, it is a lot of work, and some money, neither of which are required. A working filter is perfectly capable of doing the same job for free with minimal effort on the owners part. And finally, there are cases where floc simply doesn't work, though that is rare. We only recommend procedures that will work reliably and for everyone, floc doesn't met those criteria.

Finally, test strips, no matter the brand, have a long history of being wildly wrong on occasion and never very precise even when they are working correctly. Using imprecise information, or worse completely wrong information, makes taking care of a pool more difficult and ultimately more expensive. We only recommend using test strips for borate (and occasionally salt), where precision doesn't matter much and there is no viable alliterative test.

 

[chem geek]

Re: I still have a cloudy pool

Removing algae from a pool is a two step process. First you have to kill the algae. The next step is to remove the dead algae from the water. A sand filter will not catch the really fine particles of an algae bloom. That is why you add a clarifier to the water to help those algae particles clump together so the sand filter can catch it. The other option is to floc the pool, turn off the pump, and let the floc carry everything to the bottom. Then vacuum to waste and get rid of the dead algae.

Using a clarifier will take 4 to 5 days. Using a floc will take 24-36 hours. A quart of floc sells for $21.95, a quart of clarifier costs $21.95. Take your choice.

It is true that sand filters do not clear a pool as quickly of finer particles as a cartridge or especially a DE filter. However, using a clarifier is not the only way to speed up the process. One can also Add DE to a Sand Filter to improve its filtration. Normally, though, we just recommend shocking with chlorine and filtration which works most of the time without any need for additional chemicals. Shocking will oxidize some of the algae chemicals, break apart the algae, and make some of its less complex chemical contents (amino acids) more soluble while other more complex chemicals (proteins, DNA, polysaccharides, etc.) that are generally insoluble get some charge/polarity to induce microflocculation so clump together more to be able to get filtered. We also recommend skimmer socks that work well to remove pollen and other particles that tend to float on the surface (at least for a while).

A good clarifier can clear a pool that is only somewhat cloudy in 24 hours if the pump is run continuously. In my own pool, with a cartridge filter, I used a phosphate remover in an experiment (the manufacturer came over to try out their product as described in this post) and severely clouded the pool. Lanthanum phosphate is a very fine precipitate so would normally not clear quickly on its own. I used GLB Clear Blue and within 24 hours the pool was completely clear. However, I was willing to pay the price of the clarifier because my wife wanted to swim the next day so I was in a hurry.

If a pool store recommends a good clarifier and it works to clear the pool quickly, then that is a cost/convenience tradeoff that is reasonable. However, if you read many posts on this forum you will find that clarifiers and flocculants are recommended far too often and that they do not always work to clear the pool. A lot of the time it's because the pool isn't sufficiently shocked with chlorine to completely kill off the algae so it continues to grow while other times it's because inferior products are recommended or the source of cloudiness is not due to particles that a clarifier will consolidate.

The biggest problem in most pool stores is a complete lack of understanding of the relationship between chlorine and Cyanuric Acid where many think that CYA levels don't matter. The other big issue is that many don't do proper testing, most especially for the CYA level.

 

[chem geek]

HTH test strips are not the top of the line. HTH was good company until it got bought and sold a few times. Aquacheck is one we like. We maintain about 600 pool customers and don't have a liquid test kit on the place.

As you can see from this post test strips don't have the resolution, let alone accuracy, one needs for proper maintenance of the pool. I certainly hope that you aren't servicing any plaster pools because your test strips are only testing for Total Hardness which is irrelevant (it includes magnesium in addition to calcium) because you need to be testing for Calcium Hardness (CH) to properly calculate the saturation index to protect plaster surfaces, pool plaster which contains calcium carbonate that dissolves if the pool water is not saturated enough in calcium carbonate. Though some test strips are better than others, none are particularly good at the CYA test and certainly don't have good resolution for that test.

If you read posts on this forum, you will see how horribly poor test strips are, including Aqua Chek though they tend to be better than most and is why we do recommend those for the salt test (though even that has problems for some people -- the Taylor K-1766 drop-based test is more reliable even in that situation).

 

[Alaska Mike]

I still have a cloudy pool

Split from this topic because we were sidetracking the OP's topic.

I would respectfully disagree about sand wearing out. My opinion comes after 15 years in the pool business, and tearing down hundreds of sand filters. Several factors contribute to sand wearing out. The number one reason is the filter is not matched to the pump. Unscrupulous pool dealers sell you a 1.5 hp pump, because that is what their competitor specified, but they couple it to a sand filter that is too small, so they can save money. Then the sand is moving much faster through the small filter, than it was designed to handle. The number two reason is, the filters today are designed and called a "high rate sand filter". That means, hydraulics engineers have designed the filter to handle the highest rate of water it can possibly handle, to cut down on filter size and the amount of sand, thus saving money, but still filtering the water to accepted standards. "High rate" means it is running as fast as it can. Take your family car, and run it as fast as it can, and it will wear out, in about 5-7 years, just like sand.

Simple test is to open your sand filter. Take sample of sand and roll it betwee you thumb and forefinger. If the grains of sand roll, the edges are worn off, the individual grains of sand no longer fit as closely together, as when the sand was new. If the grains of sand don't fit tightly together, then the sand's ability to filter really small particles is greatly diminshed. Will it still filter? Yes, it will fiter something, but not the really small particles, which contribute to cloudy water. If the grains of sand "flop" as you roll them between thumb and forefinger, the edges are still sharp and angular. The grains fit together closely, and filtering is at it's best.

Face it, 3 bags of sand will take care of most above ground filters. Even at $8 per bag over 5 years, you are only spending about $5 per year to have a premium filtration system.

 

[Bama Rambler]

Re: I still have a cloudy pool

Mike, ever visited a beach? If your theory were true there'd be nothing but tiny balls and dust on the beaches. Sand gets beat up a lot more on a beach than it possibly could in any filter. There are also microscopic pictures on this site of new and old sand that was in a filter many years and there is no difference in the two.

Take a little while to look around and educate yourself before giving bad advice.

It may not be but a few dollars but why waste them if it's not needed?

 

[Alaska Mike]

Re: I still have a cloudy pool

No, I am sorry, I have not seen the pictures of sand on this website. I will try and find those and review them. Yes, I have been to the beach. I have been to many beaches on 4 different continents. I have a rather extensive sand collection from the places I have visited. I taught earth science for twenty years, and I am well aware of the processes that turn boulders into rocks, and rocks in to sand, and sand into dust. Now that is a rather lengthy process, probably decades or even centuries.

But if I followed your logic, my next woodworking project should only require one piece of sand paper, and it should last a lifetime. Now we know that is not true. I am not questioning your findings. I am sure your conclusions are valid, based on your experience. I was only hoping to add to the discussion, based on my experience, and let others benefit from our combined expertise.

 

[linen]

Re: I still have a cloudy pool

Your sand paper's sand releases from the backing and is no longer there...it has nothing in common with pool filter sand.

Here are the pics bama refered to: http://www.troublefreepool.com/sand-filter-expert-help-t30049.html#p247326

 

[chem geek]

As shown by this 1926 paper, the issue of the rate of wear of sand grains is not a newly investigated issue. This old paper implies that the rounding of sand grains is a very slow process. Here's another old paper. Note that the water flow rate in sand filters is very slow. Slow-rate is 0.1-0.4 meters/hour. High-rate is 5-20 GPM/ft² or 12-49 meters/hour (about 8-32 inches per minute or 0.13-0.53 inches per second). Water is not rushing through the sand filter and is only agitating some of the sand during a backwash which is relatively brief.

 

[Retep]

Slow-rate is 0.1-0.4 meters/hour. High-rate is 5-20 GPM/ft² or 12 meters/hour (about 8 inches per minute). Water is not rushing through the sand filter and is only agitating some of the sand during a backwash which is relatively brief.

"Slow- rate " is faster than 0.1-0.4 meters/hour. You probably meant to say 1 - 4 meters/hour , and even this speed is very very slow.
Drinking Water Plants run their Filters at about 7 meters/hour.

"High-rate" is up to 20 GPM, which means not 12 meters/hour but 48.80 meters/hour.

I also agree with the OP that Floc is very important to achieve good water clarity.
Also I keep reading that Pools need to be shocked. . . Ask yourself - Isn't that already an admission that something is wrong with filtration ?
If a Pool uses proper coagulation/flocculation it never needs to be shocked.
"Floc - don't shock"

 

[duraleigh]

I also agree with the OP that floc is very important to achieve good water clarity.
Also I keep reading that Pools need to be shocked. . . Ask yourself - Isn't that already an admission that something is wrong with filtration ?
If a Pool uses proper coagulation/flocculation it never needs to be shocked.
"Floc - don't shock"

My pool, and thousands of others on this forum, are kept crystal clear without the use of flocculant. Anecdotal evidence over the years here indicates floc results are dubious.....sometimes helpful and sometimes not.

Normal BBB procedures never call for the use of flocculants because proper filtration and FC levels never let suspended particulate int0o the pool water to begin with.

While flocculant can be used sometimes as more of a "last resort" to speed up clearing a pool, I see no reason to suggest it as part of routine maintenance.

Additionally, many people on the forum go through an entire swim season without shocking their pool except at startup

 

[UnderWaterVanya]

Try cleaning the sand when it fails your test then do a double blind test to see if it its different from new...

I suspect that the old sand is just dirty and oily.

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[UnderWaterVanya]

Floc is an interesting topic. Most seem to talk about it as something added to the water and the vac to waste... But from what I read it can be used in the sand filter like DE.

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[dmanb2b]

I also agree with the OP that Floc is very important to achieve good water clarity.
Also I keep reading that Pools need to be shocked. . . Ask yourself - Isn't that already an admission that something is wrong with filtration ?
If a Pool uses proper coagulation/flocculation it never needs to be shocked.
"Floc - don't shock"

I will respectfully disagree. An accurate test kit and proper water chemistry with adequate residual sanitizer are far more important to acheive water clarity than use of Floc. There are thousands of temporary pools out there with very ineffective cheap filters that are able to maintain reasonably clear water with just adequate FC/PH maintence and daily circulation.

Shocking a pool is a process and is only required if the water chemistry suggests it (eg. CC reading above 0.5ppm) or when one is not able to pass the overnight FC loss test described in pool school. Like duraleigh, I have never shocked my pool mid season unless for some reason I got lazy with FC maintence or one of the kids had an "accident" in the pool.

Every time I advise to "shock" a pool in order to improve water clarity is because organics are over taking over and normal FC levels can not handle that. No amount of floc will remedy that core problem unless you kill the organics first.

 

[chem geek]

"Slow- rate " is faster than 0.1-0.4 meters/hour. You probably meant to say 1 - 4 meters/hour , and even this speed is very very slow.
Drinking Water Plants run their Filters at about 7 meters/hour.

"High-rate" is up to 20 GPM, which means not 12 meters/hour but 48.80 meters/hour.

I got the info from sources such as the following, but I see that slow-rate sand filters for water treatment are at slower rates than used for swimming pool filtration.

Slow Sand Filtration - 0.1-0.2 m³/m²•h (same units as m/h). They also refer to 0.015 to 0.15 GPM/ft², but 0.1-0.2 m/h is 0.04 to 0.08 GPM/ft².
biosand filter - 0.1 - 0.4 m/h
King County Swimming Pool Code - Slow rate sand not to exceed 3 GPM/ft² (so that's 1.23 m/h); high rate sand not to exceed 20 GPM/ft²

You are right that for swimming pools most residential high-rate sand filters are specified at around 20 GPM/ft².

1 GPM/ft² = 2.44475 m/h so you are right that 20 GPM is 48.90 meters/hour so the 12 I referenced was for the "5" in the "5-20" range. I can't find my original post to correct it.

 

[chem geek]

Also I keep reading that Pools need to be shocked. . . Ask yourself - Isn't that already an admission that something is wrong with filtration ?

There is no promotion of regular shocking on this forum. Shocking is only done when there is a problem, usually algae growth which in its early stages can appear as dull/cloudy water. It is true, however, that cloudy water is not always due to algae. If it is due to a filtration problem then shocking may not help since the particles that are making the water cloudy may not be readily oxidized. Clearly if the cloudiness is due to too high a saturation index (i.e. over-saturation with calcium carbonate) then the proper solution is neither shocking nor better filtration but rather lowering some combination of pH, TA and/or CH to lower the saturation index. See 100 Reasons for Cloudy Water.

A good clarifier or flocculant can help speed up clearing of a pool when the filter is unable to quickly remove suspended particles because they are too small. So this is usually only for sand, sometimes for cartridge, and not for DE filters. For example, if one uses a phosphate remover to create lanthanum phosphate precipitate, it can take a while to clear which is why some phosphate remover products have clarifiers in them.

We've seen some pools take a while to clear and that's usually due to areas of poor circulation most commonly found in some above-ground pools such as Intex pools that have no floor drain and have only one return. A flocculant can help in this case if one can vacuum-to-waste (but such pools often have cartridge filters and no ability to vacuum-to-waste). A clarifier may not help because the fundamental problem is that a large amount of water isn't getting to the filter at all.

 

[Stuamurr]

I would just add that the majority of threads where shocking is discussed and/or advised is new users to the site tired of the runaround with various chemicals from suppliers.

Flocculant certainly has its uses, however is not required for sparkling water where the operator has a satisfactory testing, disinfection and cleaning regime in place, most seasoned users of this site have no need to shock, floc or replace sand in their filters, sand filters only become inefficient by poor operation.

Regards
Stuart