There is no set rule for what goes in a “Multi-Media” filter. The most common ingredients are sand, anthracite, Filter Ag, garnet (sometimes more than one grade), and filter gravel.
Those are the ingredients you're getting, if you're buying a replacement load for a conventional filter. However, if you're getting a new multi-media filter from us, the gravel is left out. We use the advanced Vortech tank which does not need the gravel underbed.
The media should fill the tank to approximately 18 inches from the top. If we sent a bit too much, don't overfill the tank. You should leave at least 18 inches of “freeboard,” or empty space, at the top of the media bed. The “freeboard” is an important part of the filter — the filter will not work properly without it. The filter needs the freeboard space to lift and swirl the media bed during backwash.
Below are the media supplier's suggestions for loading the filter. The order of loading is not optional, although if you get it wrong, the filter itself will eventually rearrange the bed as it backwashes. The heaviest ingredients have to go on bottom.
In other words, for rebeds in a conventional tank, pour in the gravel first, then the 8-12 Garnet, etc. For new PWP units with Vortech tank, there's no gravel, so you pour in the 8-12 garnet first, then the 30-40 garnet, etc. In either case, you should end with a foot and a half or so of empty space (freeboard) at the top. A couple of inches either way won't matter.
Bottom Layer — 12.5 pounds of filter gravel. (Conventional filters only.)
Second Layer — 20 pounds of #8-12 garnet.
Third Layer — 25 pounds of #30-40 garnet.
Fourth Layer — 35 pounds of filter sand.
Top Layer — 25 pounds of anthracite.
Freeboard — at least 18 inches of empty space on top of the final layer.
Please call if there are questions.
(whole house & well units)