Pea gravel size for filter?

[y_not]

There are other threads on this, but nothing with an answer.
It has been said that 1/8" - 1/4" pea gravel should be used as the bed for the latterals.
Found a place that sells it in small quantities by the bucket, 5gal @ $1/bucket. Seeing as I only need 50lb, will this work even though it's 3/8" pea gravel?

thx.
Tony.

EDIT: Corrected incorrect rock size.

 

[Jeetyet]

IMHO, I don't think 3/4 inch "rocks" would qualify as "pea" gravel. I believe one of the purposes of using the pea gravel to begin with is to lessen the risk of damaging a lateral when pouring it in so it follows that the smaller each stone the better. Thats my take on it anyway.

 

[y_not]

My bad, I meant 3/8".
LOL, I got the 3 right, do I get points for that?? :jocolor:

So that's only 1/8" larger than the maximum size. I would think the sand would just filter down into the gravel a bit more before "backing up", thus creating the barrier that prevents any further sand from proceeding into the gravel bed. Obviously that barrier would just be a little deeper and possibly a bit more rock in order, such that the barrier doesn't go down too far. Achieving the same effect as rock that's only a tiny bit smaller.

That to me seems what their (filter manuf.) reasoning is behind using such small rock, small spaces creates a narrow path for the sand to travel, thus a short bed depth where the sand has passed into the gravel. Hence leaving a large enough area around the lats of unimpeded gravel.

Not that I really want to debate the design and conceptual use of the gravel. Whether to use it, why, if the sand won't just simply fill it all up anyway, etc.. etc...
Not the gravel size itself when doing it. The former has been debated quite a bit here @ TFP.
I'm always game for a good, healthy debate... but too busy atm. Maybe in the winter we can all brew over it. LOL

EDIT: Slowes (Lowes) & HD, all the concrete mix suppliers, paving & gravel suppliers, quarries (yeah, we have those here) and so on just don't have anything smaller than 3/8" "pea gravel". I haven't checked with landscapers. Not too inclined to do so as I figure it's a dead end with all those other calls coming up empty for "tiny rock".

 

[Jeetyet]

Well, since 3/8 is 1/2 the size of 3/4, 8 is a multiple of both 4 and 2 and they're all even numbers as is today's date, and you identified one of the big box stores by their PROPER name, I suppose an award of 3.1416 points would be in order... this time. Just don't let it go to your head.

 

[y_not]

ROFL!
*Daffy Duck voice* Sir, Yes Sir! :tongue:

 

[y_not]

So anyone else? I'm going to pick up 50lb of this stuff this afternoon and see what happens. Filter calls for 40lb, I'll use a bit more. Most filters seem to use 1/3 anyway.

Gotta get the filter going and It's only a 150lb guy, so not the end of the earth if I have to monkey with it or abandon the gravel due to its size and go all sand.
Something tells me it'll be fine, for reasons stated above.

But hey, I'm all ears though.

 

[y_not]

I really haven't had the time to finish this project yet, weather has been pretty poor lately anyway. Still planning on trying the pea gravel @ the stated size soon.

In the interim, does anyone have any personal experience with non 1/4" gravel in a filter?
Ie. 3/8"?

 

[duraleigh]

I'll bet 3/8 is fine. I would use it.

If it's convenient, I would probably rinse it well before you put it in.

My pentair TR-140 filter listed it as an optional item as opposed to 100% sand. Although it makes sense to me, I could not find any local installers who used it so I put in nothing but pool sand. Had this forum existed back then, I would have taken the pea gravel option.

Nevertheless, my filter has performed flawlessly for nine years with original sand so I have no complaints.

I did fill the filter with maybe 1/3 water prior to adding the gravel/sand to "cushion" the impact of the gravel/sand around the laterals a bit and it may help the media distribute a bit more evenly around the laterals but that is just a guess.

 

[y_not]

Thanks for the vote of confidence Dave!
I know that phrase is typically used in sarcasm, but not here, honest!
Seriously, thanks!

I'm not a newb, but I just don't have much 1st hand experience with pool equipment in general. So It's good to hear from those that have been working with the big toys for a while.

I'll definitely be washing it off good, for sure.

That's a mighty big filter you have, how big is the pool?

 

[duraleigh]

43k. I am a HUGE fan of oversized filters. I haven't needed to backwash but once after startup this Spring.

 

[y_not]

Yeah, that's my plan for the big pool, although only 1/2 as big as yours, buy the biggest filter I can find/afford. Ie. Larger than recommended.

So is that your pool on the front of the TF100 kit, with the 2 kids jumping in it?

 

[duraleigh]

No, that's just stock photography.

 

[Bluelilly]

We used pea gravel from the lawn and garden at Lowes. It was the closest thing we could find. We certainly don't have the experience as others here but it seems to be working great. We have added DE as well and the water has been just perfect!

 

[y_not]

We used pea gravel from the lawn and garden at Lowes. It was the closest thing we could find. We certainly don't have the experience as others here but it seems to be working great. We have added DE as well and the water has been just perfect!

Good to know! All to often just doing it and doing so successfully, more than accounts for piles and years of experience.


Some questions...
So no issues with sand in the pool, or any coming out the backwash line other than a teensy few pinches at most? Does she backwash easy and well?
How about backwash cycles, that's about a 4.9sqft filter, do you only have to do it about 1x-2x/yr?
Have you had it long enough that you have passed into at least one new season and done an annual sand bed cleaning with the garden hose? Did it flush out quite a bit?
*see my Sig if you don't know about this.
Was it filtering well before the addition of de, just added it for that extra "polish"?

Thanks for the 1st hand report. I reaaaally appreciate it.
Happy TFP!

 

[CUTiger78]

If my math is correct, 3/8" pea gravel is ~3.5 times bigger than 1/4" pea gravel.

That's assuming that 3/8 & 1/4 are the diameters of the pieces and that they are perfectly spherical.

Don't know, though, if it makes any difference....

 

[y_not]

Not quite, as 1/4 can also be written as 2/8.
Take 3 and subtract 2, you get 1. So 3/8 is only 1/8 larger than 1/4.
Another way of looking at it follows thusly.

1/4" = 0.25" and 1/8" = 0.125". That's a difference of 0.125", or 50% , or an increase of half as large in diameter.
For it to be 3.5x larger, it would have to be 1-1/8". (0.25 x 3.5 = 1.125) YIKES!

In the end, its only an 1/8" larger than 1/4"(2/8").

Easy enough to get turned around on.
I totally understand, as math and I have a very rocky history. Lol

I tried to keep the boring equations down to a minimum, as I find them annoying and overwhelming. Seeing as I used to do it all in my head and got upset when I was forced to "show my work". Ugh! My downfall! :grrrr: Bad teachers! Lol

 

[CUTiger78]

Right.

But, if you assume that these rocks are perfectly spherical and that 3/8" (or .375") and 1/4" (or .25") are their diameters, you'll find that the volume, in cubic inches, of a 3/8" rock is about .028 cubic inches and the volume of a 1/4" rock is about .008 cubic inches. Given rounding, .028 is roughly 3 (maybe 3.5) times bigger than .008. :blah:

The formula is volume = 4/3 times pi times radius cubed.

But this is all neither here nor there if the 3/8" pebbles worked OK.

 

[Bluelilly]

Some questions...
So no issues with sand in the pool, or any coming out the backwash line other than a teensy few pinches at most? Does she backwash easy and well?
How about backwash cycles, that's about a 4.9sqft filter, do you only have to do it about 1x-2x/yr?
Have you had it long enough that you have passed into at least one new season and done an annual sand bed cleaning with the garden hose? Did it flush out quite a bit?
*see my Sig if you don't know about this.
Was it filtering well before the addition of de, just added it for that extra "polish"?

Thanks for the 1st hand report. I reaaaally appreciate it.
Happy TFP! [/quote]

This is our first season. I have back washed a couple of times - not really a need to due to pressure rise as our filter is rather large but just wanted to (mainly to build up a little courage that I can actually do it). I haven't had to clean the sand bed yet. I added the DE when we started with our annual inudation of pollen. It seemed to help.
As far as sand, I do see a little bit of sand/dirt in the pool; however, we live on top of a hill facing W/SW so we get all of the breeze and wind from storms, etc. so it may be just a general dumping of grit into the pool. It is so little that it's really no big deal.
I haven't added DE since last backwash and pool is very clear and sparkling. I was on float Saturday in deep end - 8' and could see the screw heads on the main drains. The DE is supposed to help with the little particles that we see at night.
I will have to update this time next year to see how it faring.

 

[Jeetyet]

...The formula is volume = 4/3 times pi times radius cubed...

In light of your great studious mathematical effort I shall now award YOU 3.1416 points as well. According to your formula posted above you had one pi already therefore you now have...

two pi,,, don't bother me,,, two pi,,, don't bother me... unkrock:

 

[CUTiger78]

...The formula is volume = 4/3 times pi times radius cubed...

In light of your great studious mathematical effort I shall now award YOU 3.1416 points as well. According to your formula posted above you had one pi already therefore you now have...

two pi,,, don't bother me,,, two pi,,, don't bother me... unkrock:

A Tams fan! Nice to know there's another beach music aficionado on TFP. And, thanks for the award.

BTW, I have eaten this morning - doughnuts. But I'm waiting for dinner...


Ah, ha, ha, ha, steak and a knife, steak and a knife
Ah, ha, ha, ha, steak and a kniffffeeee...... unkrock:

Now, back to your regularly scheduled topic.