Need guidance on Water filtration systems

[jimjimmyjimjim]

I did a search for this information but gave up after a half hour, but if you know of any threads on point pls let me know.

I have brand new stainless water tanks and I'm trying to decide on a water filtration system. I have one head, a separate shower and the galley.

Should I go whole boat system or POU under sink system?

The advantages of a pou system are that I only filter a couple of gallons a day for drinking and cooking. But the disadvantages are the under-sink space, the waste water of around 2 gallons waste to 1 gallon clean, and I'd need a dedicated pump for the filters.

The advantage of a whole boat system is that I could fill the tanks and forget about it, and since I fill my tanks from a dock hose I don't need a separate pump and I can use shore power to power the system. The disadvantage is that systems that pump a reasonable gpd are very expensive. That extra money would be cleaning water that doesn't need to be clean.

So, what have you found works best? Do you have recommendations for a water system for either POU or whole boat?

Thanks, Jim

[Bowdrie]

You'd be amazed at the "stuff" that gets/grows in the tanks over time, my tanks have inspection ports and I'm a believer.
I too fill from the dock and use one of those "Culligan" filters on the hose before the water goes in the boat.
The boat uses the whole-boat filtration with another filter like the other and the water heater and sinks get clean water.
Water heaters last longer when fed clean water.
Not really a gripe but the filters, together with the space around them needed for changing elements sometimes requires "real estate" that you don't want to lose.
Like most devices and gizmos on a boat I guess it has something to do with how much pain and suffering you're willing to trade for accessibility.
Dockside filtration pays off.

[rslifkin]

The waste water is only a concern if you go for an RO system. If you stay with just a filtration system, there's no waste regardless of how big the filters are or where you put them.

I'm just wrapping up some upgrades to my water system. In the process, I added a whole boat filter system (plumbing-wise it's after the pressure/accumulator tank and just before the hot/cold split so everything gets filtered). I plumbed things to minimize distance from the filter output to the galley faucet, figuring that's where most drinking water comes from.

As far as the filters used, I went for 3 of the big 10x4.5 housings. Filters are as follows:

• Pentek DGD-2501 (1 micron sediment filter)
• Pentek DBC-10EX2 (granular carbon and KDF)
• Pentek Floplus-10BB (0.5 micron carbon block)

I figure that any semi-decent tap water that's biologically safe going into the tank should come out tasting fine and drinkable with that system (and my tank is fiberglass, so I can add a bit of bleach if needed). Water going into the tank will also get filtered with one of the large Camco RV hose filters (rated at 20 micron for sediment removal). The carbon, etc. in the Camco filter won't do much if filling full speed (might remove a tiny bit of chlorine), so it's mostly to keep sediment out of the tank (making it easier to keep the tank water clean and fresh).

[Shrew]

What is the GPM on the 'whole boat' system??

Many water purification systems I've looked at have a much lower GPM rating (e.g. .08 - 1 GPM) than the pressure pump (3-5 GPM)

[rslifkin]

Originally Posted by Shrew

What is the GPM on the 'whole boat' system??

Many water purification systems I've looked at have a much lower GPM rating (e.g. .08 - 1 GPM) than the pressure pump (3-5 GPM)

Flow rate is why I went for the bigger filters (and I've got enough vertical clearance to switch the sumps and filters out for 20x4.5 units if needed as the filter heads are the same for 10x4.5 and 20x4.5). Even with the pressure drop through the filters, my system will flow 3 - 4 gpm (which is all the pump can do anyway once the pressure tank bleeds down).

However, the carbon filters will remove less chlorine and other stuff at high flow rates. My system should maintain good chlorine removal up to somewhere in the 2 - 3 gpm range, but 1 - 2 gpm will be more optimal for any other potential smell, taste, etc. concerns in the water. Bigger filters (containing more carbon) will increase the usable service flow rate. In my case, the highest flowing faucet on the boat is only good for 1.5 gpm, so the only times we'd flow more than that are if someone washes their hands while one of us is taking a shower or something like that.

[GreenWave]

I use the Camco-like filters when filling my tanks. I use a Brita carafe filter for drinking water. You mostly want to control sediment going into the tanks. A little chlorine in them is good. ZERO chlorine might not be best unless you have quick turnover of what you put in.

[Captain Anthony]

following

[jimjimmyjimjim]

I'm concerned about bacteria, etc. in water at harbors outside the US. So, I'm going with RO and UV purification. That's why waste water is a concern as is gpm. With a whole boat system I'd be filling at a dock, so waste would just be a cost concern. A low gpm would just mean a longer fill time. However, if I use a pou system then waste water becomes a storage issue.

[rslifkin]

For bacteria, I'd plan to work on keeping it out of the tanks in the first place. So you'd want a good filtration and UV setup to use while filling the boat tanks. Filtering down to 0.5 micron and then running the water through a UV setup should get most water to be biologically safe. And then add some chlorine to the tanks (doesn't take a lot) to kill anything that makes it through and keep any bacteria, etc. from growing in the tank. Use onboard filters to strip excess chlorine out before drinking the water.

[Tellie]

I find a POU filter is best for any water consumed, I prefer SeaGull myself. But a simple 10" filter housing with a charcoal filter on the output side of your house pressure pump will give you a whole house filtration, enough for showers laundry etc.

[Madehn]

+1 on the seagull. I have two of them.

[GordMay]

In addition to the NSF Standards for Water Treatment Systems [1], there is an EPA Guide Standard for Testing Microbiological Water Purifiers[2], which describes how to test products to determine if they are removing or inactivating the proper number of pathogens in different types of water throughout the life of the device. When looking for a microfilter or purifier ask if the product has been tested according to the EPA Guide Standard and passed. For a microfilter, meeting the EPA Guide Standard means removing 99.9% of protozoa and removing 99.9999% of bacteria in all required water types. To be classified as a purifier, the device must meet the EPA Guide Standard for the removal of protozoa and bacteria as well as virus which must be inactivated to 99.99% in all required water types.

[1] NSF Standards for Water Treatment Systems
➥ https://www.nsf.org/consumer-resourc...atment-systems

[2] EPA Guide Standard and Protocol for Testing Microbiological Water Purifiers
➥ https://nepis.epa.gov/Exe/ZyNET.exe/...kPage=x&ZyPURL

For perspective, the anthrax bacteria measures about 8 microns; giardia, E. coli, and salmonella exist in the 0.5- to 2-micron range; and viruses spread by human excrement typically measure between 0.01 to 0.3 microns, according to MSR*.
* ➥ https://cascadedesigns.com/en-ca/blo...thld-Ciey_1hYS

* MSR Water Treatment Products ➥ https://cascadedesigns.com/en-ca/col...ater-treatment

[MCilenti]

Ahoy!
I've been looking at the problem for a long time and the true expert on the topic is Drew Frye. He has a great article on his blog here:
https://sail-delmarva.blogspot.com/2...t-version.html

As well as several articles on the topic in Practical Sailor and contributes to some recent posts on Attainable Adventure Cruising (aka Morgan's Cloud).

Hope this helps!
Mike

[Kello]

IMO you are in a terrible situation.
Chlorine is the most easily available, cheapest and easiest disinfectant, but it will eat your SS tanks.
My boat came with SS tanks, they were infected with algae and I tried EVERYTHING to keep it under control, hydrogen peroxide worked the best … VERY expensive and annoying to purchase high-strength H2O2 to disinfect the tanks … AND ALL OTHER PARTS OF YOUR WATER SYSTEM, INCLUDING THE FILTERS, BECAUSE THEY GET INFECTED WITH ALGAE TOO.

What no one mentions is that the filters you choose depends on what you are filtering out. Since it sounds like you are going cruising … good luck with that problem.

POU stands for Point Of Use?? Where I currently live (marina) this area has some of the worst water quality in the USA. Therefore, I filter water for dishes and hygiene with a (many hours of research) Pentek DBC-10EX2 (granular carbon and KDF). Any water consumed for cooking and drinking also goes thru an expensive ceramic and silver and specialwhatever under-sink filter that removes fluoride, pesticides, hormones, pharmaceuticals, viruses, etc. … and hey, guess what?! The water here is so bad that even tho it is safe to drink after filtering it, it tastes so bad it is undrinkable. So for drinking and cooking I bought a small distiller, which has paid for itself many times over compared to buying distilled water, which of course comes in plastic jugs.

But your lifestyle is different as is your water situation.

FYI, if a municipal Water Quality Report is available, be aware that there are virtually infinite contaminants that haven’t been tested for – the only tests on the water are listed on the report, if it isn’t listed, it wasn’t tested.

IMO, SS tanks are bad, aluminum tanks are worse, epoxy coated fiberglass tanks (what I built to replace my leaking SS tanks) are plastic, HDPE tanks are plastic, bladders are plastic. Plastic, oh joy: https://nypost.com/2025/02/04/health...-brains-study/

Conclusion: This is why beer was invented.

[noelex 77]

We use a 316 stainless steel day water tank for all our drinking water. This tank has a relatively small size, so the turnover is high. It is fed directly from our watermaker; the water then spills over to fill our main tanks.

The hose runs from this day water tank; the hoses are short and, of course, all opaque and food grade.

This KISS approach gives great-tasting and safe drinking water without the need for filters or chemicals.

This approach works best for boats using RO water rather than dock water, so it is unlikely to suit the OP, but it may be of interest to others who rarely visit marinas.