Does sand wear out?

[UnderWaterVanya]

[Split by moderator - This debate was split from HERE]. Keep further discussion in this thread. Thanks, jblizzle]

You should have 1/3 of the filter available for water (also called the freeboard), the rest should be sand. Take a look at the grains of the sand itself and see if they are completely rounded and smooth. If so you might need a sand change. Also, most filters have an air bleed valve, look for that. If you have one, open it when you restart the pump ,then close it when mostly water begins to exit it.

Use a microscope... I can't imagine sand ever wearing out given the lack of movement and the way sand on beaches behaves.

The other info above seems very useful and dead on.

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[PJ]

Re: balanced but cloudy :-(

I have seen remarkable progress in pools that have had cloudy water, and gotten a sand change. If your sand is the same age as the pool it would definately help. Sand does break down, mostly from backwashing. The sand on beaches btw....hasn't always been sand.

 

[y_not]

Re: balanced but cloudy :-(

Sand should never need to be replaced. It doesn't wear out, EVER!!!
It does however get coated with icky, gooey, sticky stuff. IE. oils, lotions, swimmer waste, etc...
It can also get calcium or other mineral scaling on it.
When that happens, you can clean it with MA, but be careful with it.

The above extremes should only happen to a pool that hasn't been properly taken care of, or neglected.

We have had endless, countless discussions as to the above debate. But the consensus is, don't replace it unless it's so gummed up you can't get it clean. Otherwise, do a clean & re-settling of the sand bed yearly and backwash only when it reaches 20-25% higher than your starting clean pressure. Follow those guidelines and you'll be set.

As for sand filters not getting dead algae. They will, it's just it happens slower than it would with a DE or Cart. filter. But that only applies to cleaning up a mess, as for regular maintenance and filtration. So long as you don't over backwash, you should be just fine. A dirty sand bed, cleans better than a clean sand bed. But you don't want it too dirty, such that it reduces flow and filtration efficiency. So there's a balance.

If when you're clearing up your pool, after standard methods of shocking and running your pump+filter 24/7 and cleaning as necessary. If after that you still can't get the water totally clear, or it's taking longer than you'd like. You can add some DE to the sand filter, see pool school for a how-to. But that DE is going to plug up FAAAST and when it does, you have to backwash. Then add more DE as it all exits with the waste water. So wash, rinse repeat so to speak.

But sand filters are very common and fine for everyday use. Your pool will look sparkling clean and clear once properly treated and balanced with a maintained filter. You won't be able to tell the difference between other filters, except with a pool light on at night. Then you'll see some tiny little specs floating around in the light path that you couldn't see during the day. So unless you do a lot of night swimming or entertaining on the deck, it's fine. Regular use of DE can help there too.

Does your PSI gauge return to zero when you shutdown the system?
If so, it should be good.
Replacing one yourself isn't rocket science, in fact, it's a walk in the park compared to what you just did to open up your filter.

 

[dmanb2b]

Re: balanced but cloudy :-(

I have seen remarkable progress in pools that have had cloudy water, and gotten a sand change. If your sand is the same age as the pool it would definately help. Sand does break down, mostly from backwashing. The sand on beaches btw....hasn't always been sand.

Breakdown of sand is a very very slow process, think thousands of years. Not debating you did not see improvement, but likely there were other issues going on too, such as a caked/channeled sand bed, before the sand was replaced. The sand grain wear itself under a microscope is undetectable, let alone by feel.

Below is a link to sand that was used in a filter for 10 years.

sand-filter-expert-help-t30049.html

 

[y_not]

Re: balanced but cloudy :-(

Below is a link to sand that was used in a filter for 10 years.

sand-filter-expert-help-t30049.html

I love, love that post. I have it bookmarked.
If you scroll down further, about 5-6 posts, the OP of those photos linked to above, explains the difference between the two photos and gives some more info on the usage of sand. Good stuff, worth the relatively short read.

I should have posted it, but I like to wait till it comes into more question so as not to overly inundate a new member with data.

 

[UnderWaterVanya]

Re: balanced but cloudy :-(

Below is a link to sand that was used in a filter for 10 years.

sand-filter-expert-help-t30049.html

I love, love that post. I have it bookmarked.
If you scroll down further, about 5-6 posts, the OP of those photos linked to above, explains the difference between the two photos and gives some more info on the usage of sand. Good stuff, worth the relatively short read.

I should have posted it, but I like to wait till it comes into more question so as not to overly inundate a new member with data.

I keep rereading and can't find where they say which is which - but they look so similar to me I wouldn't turn around for the difference. I also noticed that the sand sample that is "old" is 10 years old from a commercial pool with higher backwashing levels than a residential pool.

This can seem like a religious war at times - my take is that it is cheap to replace and if someone really wants to - why not. The gunk removal may be more effort than somepeople want to go through and that's perhaps the reason that some people see remarkable differences between old and new sand and some clean theirs and see no reason to ever change things out.

 

[y_not]

Re: balanced but cloudy :-(

I keep rereading and can't find where they say which is which - but they look so similar to me I wouldn't turn around for the difference. I also noticed that the sand sample that is "old" is 10 years old from a commercial pool with higher backwashing levels than a residential pool.

The OP never does say. But that's the beauty of it.

This can seem like a religious war at times - my take is that it is cheap to replace and if someone really wants to - why not. The gunk removal may be more effort than some people want to go through and that's perhaps the reason that some people see remarkable differences between old and new sand and some clean theirs and see no reason to ever change things out.

That is why I say this...

We have had endless, countless discussions as to the above debate. But the consensus is, don't replace it unless it's so gummed up you can't get it clean.

All that just about covers it.
Tells the OP sand doesn't die, but they can change it if they feel the need to. Without actually saying to clean it, or change it. See? I'm sneaky.
That way we don't have to get into some big debate on it in the OP's thread, off topic really.

So change the sand, don't change the sand. It's up to you. Either way, keep it clean, resettle it each year and call it good. You'll be fine and so will your pool.

 

[Swampwoman]

Re: balanced but cloudy :-(

Yes, I'm torn on this topic too. On one hand, Hayward recommends changing the sand every 3-5 years. why bother recommending it as a mfg if it's an imaginary concept? On the other and, my neglected, foreclosed Hayward filter cleared my mud pond like a champ this spring without my having replaced the sand (despite service guy's recommendation to do so.)

I did read somewhere that filter sand is actually "ground up" to a particular size to make it rougher and more
effective, which is why you're not to use regular sand, but only "filter sand." This makes sense to me.

So I'm beginning to think that it's a case where pool guys maybe over-reccommend sand changes as a panacea to other problems. But there may be some merit to changes after several years WHEN all the other parameters, such as nascent algae, high calcium/or calcium precipitation, use of products that cause cloudiness via precipitation (eg lanthanum sulfide as phosphate removers, sequestrates after an AA treatment) are ruled out/eliminated.

My water is absolutely crystal, but if I can keep it that way with a few hours less of filtering every day via fresh sand, it might be worth the preventative maintenance. But I just don't wanna drink the koolaid if there's no real science behind it, and microscopic pictures in that post aren't quite enough for me because I don't know enough about what a micron looks like eg. DE is known to filter to 5 microns, while sand is to 30. If someone could tell me for certain that 5-yr-old filter sand lost 50% efficacy, then changing it would be a no-brained

At any rate, for those like me on the fence about this issue, here's a step-by-step post how to do it. I'm a big believer in "first-do-no-harm" on the DIY front http://www.thomaspenrose.com/diy_filter01.htm

(note - never having changed the sand, I don't know if these instructions are perfect, but I found them to be informative.)

 

[PiratesLoveBacon]

Re: balanced but cloudy :-(

FWIW:

http://www.toysrus.com/product/index.js ... agpspn=pla

2 weeks. 2 annoying freaking weeks, and sandpaper like rocks become gems. Ask any kid...

 

[y_not]

Re: balanced but cloudy :-(

FWIW:

Original Rock Tumbler

2 weeks. 2 annoying freaking weeks, and sandpaper like rocks become gems. Ask any kid...

I sooooo wanted one of these when I was a kid. Never got one. HRMPF!
This really doesn't apply to sand in a filter, it doesn't tumble. It's relatively stationary. Except when back washing, even then it just kinda dances from what I can tell.

BTW, How do you know pirates love bacon?? irat:

 

[y_not]

Re: balanced but cloudy :-(

Yes, I'm torn on this topic too. On one hand, Hayward recommends changing the sand every 3-5 years. why bother recommending it as a mfg if it's an imaginary concept? On the other hand, my neglected, foreclosed Hayward filter cleared my mud pond like a champ this spring without my having replaced the sand (despite service guy's recommendation to do so.)

Who knows why manuf. say what they say. I have yet to figure that out other than attributing it to "CYA" and not the pool kind.
I'm sure that probably has to do with the fact that most people tend to neglect things once the "newness" wears off and it becomes a chore, instead of a joy to work on. So this accounts for that.

I did read somewhere that filter sand is actually "ground up" to a particular size to make it rougher and more
effective, which is why you're not to use regular sand, but only "filter sand." This makes sense to me.

Yup, that's correct. They crush it in an industrial scale rock crusher, then they screen it out with screens that remove grains that are too small and ones that remove grains that are too big. What's leftover is safe to use and within the filter manufacturer's recommended grain size range.

So I'm beginning to think that it's a case where pool guys maybe over-recommend sand changes as a panacea to other problems. But there may be some merit to changes after several years WHEN all the other parameters, such as nascent algae, high calcium/or calcium precipitation, use of products that cause cloudiness via precipitation (eg. lanthanum sulfide as phosphate removers, sequestrates after an AA treatment) are ruled out/eliminated.

Yes, I couldn't agree more. Don't needlessly replace it, be environmentally conscious and rule out other things 1st. Also cleaning it with a hose too.

My water is absolutely crystal, but if I can keep it that way with a few hours less of filtering every day via fresh sand, it might be worth the preventative maintenance. But I just don't wanna drink the Kool-Aid if there's no real science behind it, and microscopic pictures in that post aren't quite enough for me because I don't know enough about what a micron looks like eg. DE is known to filter to 5 microns, while sand is to 30. If someone could tell me for certain that 5-yr-old filter sand lost 50% efficacy, then changing it would be a no-brained

The average human hair is roughly 80-100 microns. They go as small as about 17 and as big as about 150 or so. Depending on who you ask.
The filtration capability is dictated by how much "space" is in between each grain as they're packed against one another. The sharp edges of the grain create for smaller gaps, more rounded edges create larger gaps.
So it's really not so much the distance between grains in that picture, but the condition of each grain, on average, relative to the other grains in the other photo.

It sure would be great to have some scientific data, using a control that shows any sort of reduction in filtration capability over the years. But I'm sure those results would simply find that it reduces by some level only in "extreme cases". Being major neglect. IE. where the sand gets so bad that cleaning it is not within the grasp of the average home owner, nor the tools at their disposal.

BTW, How old is your pool? IE. How old do you think the sand is? Just curious, as it goes to show that your water is crystal clear even with an originally questionable, neglected sand bed.

 

[chem geek]

Re: balanced but cloudy :-(

See Eventually smooth the rough edges of the individual sand gra and Floc and sand and in particular my post in that latter thread. The flow rate through a high-rate sand filter at 20 GPM/ft² is 0.53 inches per second so quite slow. Given the three old papers showing that the rounding of sand grains is a very slow process and the recent photos of sand not showing wear, I don't know why there is still a debate or controversy about this. There may be other reasons to change sand, but wear from water flow is not one of them.

As for why some manufacturers and others in the pool/spa industry make recommendations or statements that turn out not to be true, I don't think that's much of a mystery.

 

[Swampwoman]

Re: balanced but cloudy :-(

Ynot, my pool is 12 yrs old, but the foreclosed family had only lived here five of those years. The original owners were the types big on maintenance, so they may in fact have changed the sand (or knew not to The latter, I doubt it, just based on other maintenance.

I realize that geologically speaking, the rounding of sand is a centuries affair. But one of my clients is involved in third world water issues, and I do know that the WHO guidelines for even slow sand filtration (we're talking a flow of .1 gph) include re-sanding of the bed after a period of frequent cleaning of the sand in general maintenance. (eg. It's not an either/or. You clean the sand on scheduled maintenance, and every so often replace or re-sand a percentage of the sand.) I'm not sure what these % of re-sanding guidelines are based on,
or how frequently they re-grind it, etc. And maybe WHO is just drinking the koolaid too, but some day I'd like to dig up the foundation of the koolaid I realize creating potable water is quite different than filtering sanitized pool.
I believe in water treatment plants they also resand the high flo filtration systems (I think, but cannot recall for certain) but they also use a lot of flocculent which perhaps gums up the sand more. Years ago, I had occasion to deal with water, sewage and watershed management on the enviro beat and parts of it float back to my otherwise overloaded brain now and then Just not always in a particularly useful or coherent way!

water too.

 

[chem geek]

Re: balanced but cloudy :-(

The WHO document on Slow sand filtration (referenced from this link) on page 80-83 (PDF page 78-81) says the following:

Resanding

After several years' operation and, say, twenty or thirty scrapings the depth of filtering material will have dropped to its minimum designed level (usually about 0.5-0.8 m above the supporting gravel, according to the grain size of the medium). In the original construction of a marker, such as a concrete block or a step in the filter box wall, is sometimes set in the structure to serve as an indication that this level has been reached and that resanding has become due.

During the long operation of the filter some of the raw water impurities and some products of biochemical degradation will have been carried into the sand-bed to a depth of some 0.3-0.5 m, according to the grain size of the sand. To prevent cumulative fouling and increased resistance, this depth of sand should be removed before resanding takes place, but it is neither necessary nor desirable that it should be discarded. Instead it is moved to one side, the new sand is added, and the old sand replaced on top of the new, thus retaining much of the active material to enable the resanded filter to become operational with the minimum of re-ripening.

This process, known as "throwing over", is carried out in strips. Excavation is carried out on each strip in turn, making sure that it is not dug so deeply as to disturb the supporting gravel layers below. The removed material from the first strip is stacked to one side in a long ridge, the excavated trench is filled with new sand, and the adjacent strip is excavated, throwing the removed material from the second trench to cover the new sand in the first. The operation is illustrated in Fig. 26 and 27. When the whole of the bed has been resanded, the material in the ridge from the first trench is used to cover the new sand in the last strip.

In areas where the sand is expensive or difficult to obtain, the surface scrapings from regular cleanings may be washed, stored, and used for resanding at some future date. These scrapings must be washed as soon as they are taken from the filter, otherwise, being full of organic matter, the material will continue to consume oxygen, quickly become anaerobic, and putrefy, yielding taste- and odour-producing substances that are virtually impossible to remove during any later washing process.
:
It must also be remembered that filter sand, when washed, loses its finer particles, so that the effective diameter is increased. This is likely to result in deeper penetration of impurities into the bed during subsequent filter runs.

As stated above, the resanding has nothing to do with any change to sand particle size itself from any wear whatsoever. Instead, it is due to 1) losing some sand material from the filter over time, 2) the process of "throwing over" moves the sand around but is recommended to keep moved strip material and not to replace it and 3) washing sand removes some of its finer particles.

The "scraping" process they refer to is analogous to the backwashing of sand filters for pools except that they don't backwash but instead drain the water down somewhat below the top of the bed and remove the top layer of sand that contains the bulk of trapped material. As noted above, this sand may be cleaned rather than discarded. It is most certainly not "worn out".

Do you have any specific documents regarding water treatment that we can look at to further refute this nonsense about needing to replace sand due to it's "wearing out" by getting smoothed from water flow?

 

[PiratesLoveBacon]

Re: balanced but cloudy :-(

BTW, How do you know pirates love bacon?? irat:

Adam Savage (Mythbuster) said so, as they were shooting canon balls through pig carcasses...

 

[y_not]

Re: balanced but cloudy :-(

This thread wandered a little off topic.....

Gee, thanks UWV. BRAAAAADDD!!! :lol:
I said I wasn't going to start a debate and clutter up the OP's thread. *points finger*

It's OK though man, I love intellectual discussions on almost anything.

OPs, I think we should split out all the posts that talk about the sand bed wear and tare debate. leaving behind the OP's posts and the ones that relate to them. Then stick this over in the deep end.
Maybe attach it to the previously linked thread /w the sand closeup photos?

I don't know if you can do it with that level of granularity, or if it's a "one post and all following" kind of thing.
*pun not intended.

 

[UnderWaterVanya]

This thread wandered a little off topic.....

Gee, thanks UWV. BRAAAAADDD!!! :lol:
I said I wasn't going to start a debate and clutter up the OP's thread. *points finger*

Sheepish l look...yes.

Sent via Tapatalk...

 

[y_not]

Gee, thanks UWV. BRAAAAADDD!!! :lol:
I said I wasn't going to start a debate and clutter up the OP's thread. *points finger*

Sheepish l look...yes.

It's OK buddy. *pats head*

 

[y_not]

Re: balanced but cloudy :-(

BTW, How do you know pirates love bacon?? irat:

Adam Savage (Mythbuster) said so, as they were shooting canon balls through pig carcasses...

HAHA!! Adam Savage, he's soooooo awesome!!
I have a friend who's named Adam and Savage reminds me quite a bit of my friend's antics. :lol:

And why were they shooting cannon balls through pigs?
I must have missed that episode, but maybe I did see it.
I'm guessing they didn't know either. HEHE

 

[Swampwoman]

ChemGeek, I don't have any documents, and my comments about having to resand a bed were from clients discussing the phenom, but I'd never asked them why (They were/are actually developing and alternate 3rd world filtration system, because apparently it can be difficult somehow to get replacement sand in some areas...presumably filtration sand...)

So I googled this am to see if there are water treatment docs out there that mention whether or not they replace or restore sand. I took a quick glance at this one discussing filtration systems https://docs.google.com/viewer?a=v&q=ca ... 5MihOS01-w

But it's equally vague, and cites that in some cases (note, only SOME cases) the media (sand) needs to be replaced in 3-5 years and mentions disposing of the old media in a landfill. I can't tell, however, if that's laziness (eg easier to throw it out than to wash it? Cheaper?) or because with storm water there's some kind
of concern about residual contaminants in the media bed and ergo a reduction in exposure (which might be more likely.)

I'm on the iPad right now so cant seem to grab text, I think it was on page three.

But all I want to know is why mfgs recommend it, if there's something about the condition of ground sand that has them recommend the change, some lab test somewhere that shows them any distinct difference between the micron filtering capacity in their filters when the sand is old versus new once old sand is cleaned. If I get a chance at lunch I may try to write to Hayward and ask, and if by some miracle I get a coherent response, I'll let you know In general, any sand WILL filter (if clean) and of course sand is ancient. But we're not putting sand from the beach unmitigated into those filters. We're altering the sand by grinding it and controlling it's size and texture. So it's conceivable to me that they *might* have some rationale for changing it. OR, like the EPA, it could just be a matter of convenience, or based on assumptions that don't bear out. I don't know, and I don't really have a dog in the race at this point because my filter works great (and I may never have a dog in this race ) but I AM curious!