De-silting water before filtering

I have heard there is a chemical you can put in a bucket of water that causes silt to drop out (precipitate) to the bottom of the bucket.

Is it true, or camping legend? If true, can somebody please tell me what the chemical is and where to get it?

TIA ~~Chip

Powdered alum

– Last Updated: Feb-24-13 2:45 PM EST –

Used to be in the grocery store when people did more home pickling.

Could be hard to find..check old time pharmacies too.

Used it on the Yukon and Green Rivers with good results.

Size does matter. Too little or too much and nothing happens

Also used in pool maintenance.
I used to add some to the filter line to create a “floc” on top of the filter sand. Find crud would be caught, and the filter cleared by backwashing.

I don’t know if it’s still used, or whether what one might buy in a pool supply place would be OK. I’m not familiar with using it to precipitate silt, only as a filter layer.

Clean bandana
Always used a piece of cloth like a bandana

to avoid getting sediment into the filtered water bucket.

Why use a chemical method to begin with ?

Why? Because
really fine silt will not settle out completely even after waiting overnight with that Sea to Summit dishpan.

I have one of them. I waited overnight for the gunk to settle both on the Yukon and the Green.

I added the alum after waiting did not work. Yes it is a two step process.

Alum at Wal Mart
I have tried the alum technique a couple of times and it has worked well. One of the guys on our 7 day San Juan River trip developed a leak in his soft-sided water container. He used alum and a water filter to re-supply from the river. Wal Mart has an extensive collection of McCormick spices including the alum.

Pur Reliance

– Last Updated: Feb-24-13 7:30 PM EST –

On two different Yukon 1000 canoe races, we used the PurReliance chemical system to both de-silt and purify our drinking water. Did not need to filter. It worked well for us. A 6-man voyageur canoe needs lots of water to paddle 1000 miles. We purified 5 gallons at a time. Two small packets does it. I carried alum as a backup, but didn't use it.

Alum from a grocery store, as simple as that. Thanks for the info. There’s a store near me that sells lots of canning supplies, so I’ll look there for Alum.

The PUR Reliance product sounds good, too. I might have to take a couple different products and have a water “bake-off”!


We used Chlor-Floc in the Air- Force
The water was still murky but safe.

I admit to being overly cautious and pre-filtering through coffee filters before I stick my pre-filter hose into that water.

Once the river was so bad I paddled into the middle of the lake to find water that I felt was clear enough to filter.

How to YouTube

This discussion has led me to a new word.

Seems when things glob together in the water and drop out of the solution, some flocculation is going on. New word for me. Just wanted to throw it out there.


I don’t drink water
because children pee in it and fish floculate in it.

I was thinking more of glumpy
Apparently a new word to describe wet snow…how it stick together in gooey clumps.