Recommendations Please… What’s the best gravity flow filter?

[DWR D]

Need some recommendations on the best choice of a minimum 4 liter gravity flow water filter. Ones to stay away from?

Thanks

[David Gardner]

I got this one from Amazon a couple years ago, and it seems to work well. Haven’t tested for water quality, but never any GI issues using it.

Slightly off-topic: With all the recent reports of testing showing that PFAS/PFOS forever chemicals and nano-plastics are everywhere, from the bottom of the Mariana Trench to the top of Everest, in rain, fog, sea mist and ground water, I’m patching together my own gravity system using filters from Clearly Filtered, which eliminate those from your drinking and bathing water. In addition to their other systems, they make water bottle filters that look like they can be adapted to use a variety of filler bags/containers. I have ordered a couple and will report on my results.

[Jerry Adams]

off topic – I read that water filters shed plastic particles and chemicals – you’re better off drinking tap water

I don’t think there’s good information about this, like is there any significant risk to our health

Lots of sensational headlines like how many particles of some size there are.  Sensational headlines to get us to click on stories so they can make money off ads.  And if they don’t do this they’ll go out of business so I sympathize.

on topic – I’ve used sawyer squeeze in gravity mode.  It worked fine.  I find it easier to just use it in squeeze mode.

[Dan]

The Platypus Gravityworks 4L kit is not the lightest, but very robust and convenient to use.

Obviously, you can assemble a gravity filter from components using virtually any filter, I’ve done it with Hydroblu and Sawyer filters with success, the former is currently my go-to. They all have their pros and cons (weight vs. flow-rate vs. fouling vs. ease of use, etc.), so it’s hard to say what is “best” without understanding your criteria better.

[David Gardner]

Whatever plastic the Clearly Filter sheds, it is far better than virtually any tap water. And it is the only filter I know of, although there are likely others, that target forever chemicals. If you are out on the trail getting water from lakes and streams, it has PFAS/PFOS in it. Everywhere in the world. The EPA and I think the UN too recently issued a statement saying that rainwater is not safe to drink anywhere in the world because of them.

Plastic is bad, but PFAS/PFOS are much worse. The EPA has set standards for PFAS/PFOS that were in parts per billion, but is about to announce new standards that will be required for drinking water across the US of 4 PPT – 4 parts per trillion – equivalent to one drop of water in FIVE Olympic-size pools. These chemicals are endocrine disruptors that f. with hormones, especially in children and adolescents, and are believed to be the cause of various types of cancer as well. And for all practical purposes, measured in terms of multiple generations of humans, they never go away.

[DWR D]

Hey, guys… the micro plastics and forever chemicals topic is very interesting and important… maybe one of you could start a different thread just for that…. I already had one thread hijacked to the point I was getting not getting the recommendations I was asking for on best/recommended gravity flow filters… would appreciate getting back to that? Thank you… no offense intended… :)))

[David Gardner]

Yeah, sorry.

MSR also makes a 4L gravity filter system.

[Jerry Adams]

we offer penance by actually answering your question : )

[DWR D]

lol Jerry…. lol…

[JCH]

I have a 4L diy gravity system using the original sawyer squeeze that I am completely happy with.  Cannot recommend either the sawyer mini or micro…vastly inferior to the OG in virtually every aspect for only a 1 oz weight reduction.  Other filters may be faster in gravity mode but the squeeze is reliable and predictable

A friend has the 4L gravityworks system and is very happy with it.

[Jerry Adams]

Good, DWR isn’t sore about it :)

When I did gravity mode with sawyer squeeze I got distracted and it filled up and overflowed the output container.

1 gallon container of untreated water, 1 pint container that I gravity flowed into.

[Dan]

I should have said that I also have firsthand experience with the gravityworks 4L and it works very well. It’s ready to go out of the box and it’s well thought out with quick-connect valves, etc. The bags are very strong and have good closures. I’ve used the same filter for many years. You just need to burp the filter, back-flush occasionally, and clean with dilute bleach before storage. I’ve had it for many years and still use it when my wife and I go on trips together. I think it’s overkill for one person, but my wife loves how convenient it is to use and she’ll take it on solo trips.

You could save a couple of ounces with a DIY system by using lighter bags and fittings, and a Hydroblu or Sawyer filter. You’ll find systems like these described in various places on the internet and probably on the forum. Conceptually they’re simple, but you need to assemble the components and fittings, sometimes you need an adapter or two. I’m sure many of us would be happy to show you what we’ve assembled if you decide to go that direction.

[DWR D]

Great information Dan! Thanks…. In my case, there are going to be two people. Even when solo, when camps are far away from the water source, I often take enough bottles to bring 1 gallon or more back to camp so I don’t have to keep making the trip back for more water. Can… can you tell me if that 4 liter dirty water bag would travel well in a day pack back to camp? or better just to carry in my hand?

Thanks

[DWR D]

It looks like that Gravity Works dirty water bag has some kind of zip lock opening at the top. I wonder if that is a dependable seal that would not leak in a day pack when bringing it back to camp?

[Terran Terran]

Two Sawyer filters. Four 2 liter CNOC bags. You’ll have a 4 liter setup cheaper than the Gravity Works. You’ll each have your own set up. It will be redundent in case 1 filter fails.. The flow will be twice as fast.

[DWR D]

Interesting idea TT…

[Dan]

The gravityworks dirty bag has a zip lock type of seal, but it’s a LOT beefier than a normal zip lock seal. It takes some finger strength to close it (and open it), but once closed properly I do not recall ever having a leak and I think that would be unlikely. After closing it, I invert it to make sure it’s sealed. On occasion, I’ve carried water in it for a mile or two in a pack to set up camp.

I agree with TT about CNOC bags being good for a DIY system, and you can also squeeze them. However, they are quite delicate in my experience. They are easy to puncture and you can also get pinhole leaks around the cap. Personally, I use a CNOC bag for dirty water because they have a wide mouth and are easy to fill. When I hang it, I’m really careful not to puncture it on something sharp (like a twig or broken branch), and then I put it away. I prefer to use something stronger (like a platypus bag) for the clean water because it’s generally being used around camp.

Also, note that to get a good siphon effect, you want to have a substantial hydrostatic pressure head. So you really don’t want to just have bag-filter-bag. A length of tubing is very helpful to increase the flow rate.

[DWR D]

More good info Dan… so talking of various kinds and sizes of bags.. do the GravityWorks connectors fit a) all Platypus bags they make? and b) the CNOC bags? Other brands of bags? [I am a fan of Platypus bags… have been using them for decades and have a selection of them… I find them pretty durable… don’t thin one has ever leaked inside my pack]

thanks….

[Bob Shuff]

I made a diy gravity system with an ultralight 10L silnylon dry bag. Worked great until one of my scouts didn’t roll the dry bag and tried to lift about 5 liters holding the clips. The bag tore and we were back to using the small mylar bag that came with the squeeze. I replaced it with an MSR Dromedary 4 or 10L bag, much heavier, but bombproof.

The benefit of the gravity system is you can set and forget, so the more volume the better. Just don’t underestimate the weight of that dirty bag.  MSR makes a 10L with and with an option that includes a carbon and virus cartridge. I have not tried it, but sounds interesting. I know you can buy a carbon filter cheap, but not sure how the virus cartridge works, or when you need to replace it.

[Dan]

If I recall correctly, the clean side of the gravityworks setup is pretty generic. The tubing fits on hose barbs, the filter on one end and the cap on the other end, and I think that the cap would screw onto any standard bag. However, the dirty bag has a quick connect with automatic shutoff, which is obviously very convenient because you can fill it, hang it, and then connect the rest of the system. I don’t know if other platypus bags have that same connector.

[DWR D]

odd that the 4L GravityWorks system has the inlet of the clean water bag on the bottom… any reason you can think of that you could not hook up that clean water connection to the top of a top inlet Platypus bag???

[Todd Stough]

I have the Platypus gravity works also and I’ve been a big fan of it.  Sometimes I need to fiddle with it a bit to get the flow started, seems like air gets trapped, normally the first use after not being used in a while.

I assume the clean bag has the inlet at the bottom so you could keep it in a pack and fill it in place, then swap on a valve.  The zip top dirty bag works great, it is easy to fill and seals well, although it is a little stiff to seal when cold, near freezing.

[Dan]

Bottom/top is arbitrary. When you say that the inlet of the clean bag is at the bottom, I assume you mean that it’s opposite the strap? Otherwise there is really no functional bottom or top because it has only one opening. When filling the clean bag you would orient the opening at the top. While the strap isn’t necessary, if you are going to hang the clean bag, you definitely want the outlet at the bottom so that you can dispense water using the pinch valve. That can be convenient for one-handed operation of such a large bag. If you wanted to save weight, you could remove the strap.

And yes, I think you could easily use a different Platypus clean bag.

As Todd mentioned, you need to burp the filter to get air out, this is clearly described in the instructions. You do this by filtering a small amount of water and then lifting the clean bag above the dirty bag.

[Jon Fong / Flat Cat Gear]

OK, so this is for car camping right?  Why not get two 5 gallon buckets and a Sawyer?  Put the dirty water bucket on top of your car a siphon the water down to the filter and discharge it into the clean bucket.  I would think that speed would not be an issue.  My 2 cents.

[Terran Terran]

The Sawyer is slower because it has smaller pores and filters better.

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