Sand filter and broken lateral

[waste]

I clearly recall putting 'pea gravel' into any sand filter, up to about 1/2" to 1" above the laterals before adding any sand. Al is certainly right about having water in the filter before adding sand (and, as I suggest, 'pea gravel'). Perhaps it's because adding the pea gravel might hide a broken latteral. However, I recall the PacFab Triton (?) filters recommending doing this.
This makes sense, the top 12 - 24" will catch as much "stuff" as an extra 1" (or so) will, and you get a less constricted flow around the latterals. (And if a lateral breaks the sand into the pool will be lessened, perhaps allowing the owner to postpone a lateral replacement a season)

[duraleigh]

Interesting. I talked to the Triton folks when I filled my TR-140. The instructions called for pea gravel as well but were VERY unclear as to whether it was essential.

My end result was to not use the gravel. No one could tell me it was essential in a way that convinced me. The pros in my area (I called three) don't use it and two hadn't heard of it.

I sorta' ended up thinking the sand filled around the gravel very quickly, not doing much to alter the filtering characteristics.

This is not to dispute "Waste's" thinking but simply to post how I arrived at a different conclusion....I have no idea if one makes more sense than the other.

Matt, You finally found a scenario where I agree with replacing the sand (We've discussed that before, I think) It would be such a hassle to salvage and reload the old sand.......new in the bag makes more sense.

Al, my good ole' Triton has a clever valve on the bottom that allows you to release only water or both water and sand. My assumption is that in the "sand" position it would allow you to wash the sand out with a hose....seems like it wouldn't be too bad but I've never tried it. Am I missing something?

Dave S.

[waterbear]

Putting a layer of corse filter mateial (pea gravel) in befoe the fine filter material (sand) is an effective way to filter and is pretty much standard in any aquarim filter setup. The sand will not "fill the holes" but will pretty much stay in it's own later. This will allow a better water flow through the laterals with less chance of them plugging with sand, will help reduce the chance of lateral breakage, and should give you more effecient filtration overall. It probably is not necessary but IMHO is a good idea. I am wondering if anyone has ever done it both ways to check the difference in a pool filter. BTW, sand filters similar (sometimes identical) to pool filters are used to filter large commercial aquariums for mechanical filtration.