Depends on the water source. If it's a clean river (not silty desert water), I highly recommend a Katadyn base camp gravity filter. Fill the bag, hang the bag, go do something fun while it does the work!
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Family of 3 you could just carry it. Really depends on the trip. Lodore and Yampa you can refill part way through. Deso we just grab water out of Rock creek and treat with Aqua Mira or iodine. The Grand renting a bad ass electric pump filter makes sense. I'm about to do Cataract with 20+ people and we are going to take our time so I'm planning on water wizard, then a Vital gravity pump, and aquamira. A bag system might be fine for somewhere with clear water. Comes down to what you are doing and how much you want to spend (like everything else )
I've used it for years on smaller group river trips and backpacking. You would have to settle silty water first, with alum or other chemicals in a bucket. This filter system is lightweight and fairly fast. There is some maintenance when you get home, cleaning and drying the filter.
I love those gravity bag systems. Easy! My present addition to my gear pile is this: Note, it is not finalized but the system is based on using more readily (cheaper) parts. For the anti bacterial part I am using a Doulton ceramic house filter. Before that I will use a home depot particulate/charcoal element. I have mad a pump using PVC. Sort of a longer skinnier raft pump. This set up is a lot cheaper than the expedition filters and has easy to replace stuff.
I wanted to build a system with a filter followed by a UV purifier but was having trouble finding a reasonably priced 12v model. I have the pump & filters to do a couple gpm.
I've rented them for GC but that's about the only place that seems to rent them. I'm doing the Salmon in a couple weeks with 30 people so it would be nice to have 1 on that trip. We plan to carry a bunch and then resort to a gravity filter.
I built a 12 v pump water filter/purifier. It fits in a pelican case, has a solar panel and solar charge controller, 12V 12 AH sealed lead acid battery. It runs with a 1 gpm shurflo pump and then through a 0.5 micron carbon filter, then a Dalton 0.9 micron absolute ceramic filter. We then run a UV filter off of a 12V modified sine wave inverter to get rid of any viruses and anything that is left over.
I was concerned about the UV output using a cheap 200 W modified sine wave inverter so we ran it across a scope to make sure the UV output was the same. We also used a buck to lower the voltage to the inverter. It didn't make a difference. The voltage and amperage at the bulb were the same whether I used the modified sine wave inverter, wall or pure sine wave inverter. Voltage drop to the modified sine wave inverter didnt change the output either.
It has been down the grand already and is headed out on another trip. Easy build. I also built one to fit in a rocket box for a friend. Not a super cheap build but works great!
We refer to it as "the bomb". It is surprisingly heavy too. The shurflo pump and battery really add some weight. When the 2 filters are full of water its weight is probably close to that of a 5 gallon water jug.
I had a PM asking about cost for the filter. The filter was a fair amount of work to build and it wasn't cheap but nothing worth while usually is. These are just estimates. You will spend more/less depending on what you buy.
-12V, 12-14 A sealed LA Battery $40-60 depending on what you buy
-20 Amp Solar Panel $30
-Solar Charge Controller $20
-Misc switches/fuses $25-$50 depending on what you buy
-Waterproof Electrical aviation connector (plug in solar panel when box is closed so it can charge on raft) $15-$70
-UV filter $70
-Water Filter housings $25 each
-Shurflow Pump $100 (a friend built one with an Chinese amazon special pump for $20 and brought a spare on his Grand trip)
-Doulton Ceramic Water filter $32
-Carbon block pre filter $15
-Compression fittings for water $15
-The 3/8 and 1/4 auto shutoff/quick connect fittings were pricey, $30 each? dont remember how much they were but you could do without.
-Shut off valves for intake and output $16
You also need a case to mount it in, Either an Ammo Can or a Pelican case.
Some type of board/aluminum to mount everything to. We bent a custom piece of 12 gauge 5052 aluminum to mount everything to and I had some scrap angle to finish it off. The aluminum also bolts to the tabs inside my box to keep it all in. Misc electrical wire, wire connectors, nuts/bolts for mounting
Sorry too lazy to add it up. Probably don't want to know either.
Some have asked for a schematic. It's pretty simple - water in to pump (the diaphragm pumps self prime) then to carbon pre-filter, then to ceramic filter, then to UV sterilizer.
Electrical is easy too. The Solar controller has solar in +/-, Battery +/- and Load +/-. I added labels to the switches after I took the picture.
The UV light should be turned on for 2 minutes before you pump water and I discard a quart or 2 when we start pumping each time to get rid of the stale water. Take the filter apart when you get home and dry them out if it is going to be a while before you use it again.
Harbor Freight now sells Pelican case knockoffs. I haven't tested their waterproofness, but intend to. They have a manual rather than automatic air pressure relief port. There are several YouTube video reviews.
I've also played with sealed lead acid batteries for various cordless music solutions over the years. I don't like that they typically only last 3-4 years worth of charge cycles. I'm REALLY impressed by the LiIon battery packs you can buy on eBay: https://www.ebay.com/itm/DC-1298A-D...m=273349914107&_trksid=p2047675.c100005.m1851
Two of these would have a similar cost to a single large-ish SLA battery, but weigh substantially less and also last longer.
Depending on the source of the water where you go. I suggest using Sawyer's B0899 NW4 Gravity Water, which I usually bring with me when I go on a picnic or adventure. Very good filtration, delicious and cleaner water than bottled water.
I made a uv filter setup that fits in a rocket box. The battery pulls double duty charging unit for devices and the filter. Looking into upgrading to a lithium. Also have a katadyn expedition for back up.
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