underbed gravel question

the unit I'm looking at purchasing from ohiopurewater.com 2510SXT 48000 Grain Capacity does not come with gravel for the bottom of the bed. I nee to know how much to get and what kind to get. They sale a bag of 5 - .05 cu/ft Bags of Red Flint gravel for $85. That seems a little too high to me.. Any help in thiss?

I wouldn't buy a softener without a gravel underbed. It should be 1/8" x 1/4" (round edge) stone IMO. The amount depends on the size of the softener but most don't need more than 20 lbs and the majority, less than that. It should cover the top of the bottom basket by about an inch.

Underbedding is used for a couple of reasons. One to try and prevent channeling and the other is to keep the bottom distributor from expanding. Most unit will have it. I think you would be better off with it, but the cost you quoted is too much. The cost should be around 20 cents a lb.

Well, I got them to throw the gravel in the order.

They insisted that it is not needed. That the manufacurer of the resin claims they don't need gravel, but to make me happy he threw in 15 pounds of it. I guess it won't hurt anything to put the gravel in?

Also does this mean I need to use less of the resin or will it just come up higher in the tank with the gravel down there?

I'm installing a 4800 grain 10x54 resin tank 1.5 cu ft of HIGH CAPACITY resin with a Fleck 2510 valve.

Use the same amount of resin. The error is settings would be negligible. Make sure you have an upper basket to prevent resins from backwashing out.