Sterilizing water in developing countries

[Letterkenny]

Wanted to see what people use to sterilize water going into your tanks when cruising in a developing nation. We are typically in Southern California and drink the water in the tanks first by prefiltering with the standard camco and after filtering with my Larq water filter that also has UV. I also bought a UV water bottle cap that fits the wide mouth hydro flask type bottles. I believe the carbon filtering is necessary for taste purposes but neither required for the city water we have.

However, we will take the boat to Ensenada this fall. I have heard that you can have locals fill the tank with the 5 gallon jugs of water but wanted to plan in case not possible. Would my current setup be sufficient or would you want a better tank prefilter, such as the Clearsource Ultra with virus guard (curious how this works), a RO system, or a combo carbon and UV set up? I suppose the last option would be to just use the 1 gallon jugs for drinking and sterilizing the tank after.

[sailormed]

The little chlorine tablets from your local pharmacie do a great job.

[StuM]

Depends on what developing nation and where in the country. I've been drinking Port Moresby tap water with no filtration for 30+ years with no problems.

[wholybee]

x2 on chlorine tablets. The CDC and WHO both recommend chlorine. Bottled (be sure it has no additives/perfume) works also. Their other recommendation is boiling, but that isn't usually practical. Excepting a water maker, I don't trust any filter, especially at a flow rate high enough to run a tap.

The 5 gallon jugs are readily available at every port in Mexico-cheap.

[ejs]

We used a combo filter and UV to filter the dock water in Mexico. If you are going farther afield you'll need an RO water Maker eventually. Easier to do it in the US than in Mexico and then you won't need to worry about the dock water.

[motion30]

I use a watermaker. Never worry about the water I drink

[thinwater]

Remember that no pre-filter or UV is 100% and they will not prevent bugs from growing in the tank. This is why WHO and EPA specify a chlorine residual in the tank.



Drinking water is a multi-step process. Pre-filter to remove dirt, clean your tank since nothing dirty can be sanitary, filter the vent so bugs don't fly in (it's in the plumbing code), treat the water, and and then post filter for cysts. No one magic bullet.



Sail Delmarva: Drinking Water Filtration--The Short Version

[rslifkin]

Originally Posted by thinwater

Remember that no pre-filter or UV is 100% and they will not prevent bugs from growing in the tank. This is why WHO and EPA specify a chlorine residual in the tank.



Drinking water is a multi-step process. Pre-filter to remove dirt, clean your tank since nothing dirty can be sanitary, filter the vent so bugs don't fly in (it's in the plumbing code), treat the water, and and then post filter for cysts. No one magic bullet.



Sail Delmarva: Drinking Water Filtration--The Short Version

Agreed. Ideally I'd want a fairly fine filter to get rid of sediment, a carbon filter to at least reduce other junk in the water, then UV sterilization. Then put the water in the tank, add some chlorine so it stays clean and doesn't grow stuff. And then the onboard filters should take care of the rest (we filter to 0.5 micron on board including 2 different carbon filters).

[wingssail]

Originally Posted by Letterkenny

Wanted to see what people use to sterilize water going into your tanks when cruising in a developing nation. We are typically in Southern California and drink the water in the tanks first by prefiltering with the standard camco and after filtering with my Larq water filter that also has UV. I also bought a UV water bottle cap that fits the wide mouth hydro flask type bottles. I believe the carbon filtering is necessary for taste purposes but neither required for the city water we have.

However, we will take the boat to Ensenada this fall. I have heard that you can have locals fill the tank with the 5 gallon jugs of water but wanted to plan in case not possible. Would my current setup be sufficient or would you want a better tank prefilter, such as the Clearsource Ultra with virus guard (curious how this works), a RO system, or a combo carbon and UV set up? I suppose the last option would be to just use the 1 gallon jugs for drinking and sterilizing the tank after.

Our approach has been simple: A single stage pre-filter (10mic) before the water comes on the boat. Then (after chlorine treatment if we feel it is necessary) a 1 micron carbon filter for the cold water tap in the galley which we drink. That's it.

We have a watermaker, but we still fill the tanks with 140 gallons of water wherever it is available. Since we live aboard full time (year 'round) and use a lot of water the water in our tanks gets refreshed quite quickly.

This approach has worked for us for 38 years. No water born illness or other problems. And it is simple.

[Jammer]

Overall, Mexico has water that is safe for drinking, no different than the USA and Canada. The main problem anywhere is keeping it that way as fixtures, hose ends, and especially jugs are easily contaminated during routine handling. As posted upthread, chlorine treatment is the gold standard. City water supplies will have chlorine already added so unless you filter it out with a carbon block you will have some chlorine in the tank.


It's a good idea to filter for sediment as you fill the tank but it's a hassle. The camco filters are counterproductive, they only filter to 100 microns for sediment which isn't enough, and the carbon block takes out the chlorine. I use 1 to 5 micron filters in a standard 10" housing which are bulky but effective and inexpensive.


If I am using well water that has not been chlorinated I add 1 mL of ordinary household laundry bleach per gallon. With water that has been filtered for sediment so that there is no suspended organic material this should be sufficient with a reasonable contact time (1 hour or so) in nearly all cases. There will be some chlorine aroma in the water which some people find objectionable.


There test strips available from various sources to more accurately measure the residual free chlorine and adjust the dosing, and there are some US government articles with charts (USDA, EPA, FDA, I can't remember which). In most cases this would adjust the dosing downward from 1 mL/gallon of bleach. There are several problems with accurate dosing: the amount of chlorine in household bleach varies from jug to jug, the pH and temperature of the water affect the free chlorine required, and the chemistry and organic material content of the water affect the amount of chlorine that gets bound and becomes useless for disinfection. Using the test strips, combined with a pH test and a temperature measurement, allows using the minimum possible amount of chlorine, while still producing safe water.


I don't do this because it's difficult to do at a small scale when filling tanks. If you miss on the low side while filling the tanks it is difficult to add chlorine and agitate enough to distribute it evenly in the tank, and if you miss on the high side you have to dump out half or 3/4 of the water (or whatever) and refill.



The UV setups do work but the portable ones are a hassle to use on an ongoing basis, and the large ones that can do a whole tank require a good deal of electrical power and have low flow rates.


For a while, point-of-use microstrainers (sub-micron filtration, usually using a cermaic block) was a popular approach that was particularly effective against giardia and some of the other parasitic organisms that are particularly difficult to control with chlorine. They also control bacteria (but not viral pathogens e.g. Hepatitis or Norovirus). Seagull was/is the major vendor. They're expensive and have low flow rates.

[Jammer]

Originally Posted by wingssail

This approach has worked for us for 38 years. No water born illness [...]

I think your approach is sound, but, regarding water borne illnesses, how would you know? 38 years without a single bout of diarrhea?

[rslifkin]

The extra large version of the Camco filter I'm using is listed as filtering to 20 microns. I figure that's adequate for keeping most junk out of the tank from a good water source. It does have carbon and KDF in the filter, so I add some chlorine (bleach) back to the tank after.



If I were somewhere with more questionable water, I'd trade the Camco in for a 2 filter + UV setup (with some kind of housing to make it easier to carry). Probably a 1 micron sediment filter and then a carbon filter before the UV, then add some chlorine to the tank. If you've got carbon filters of adequate size on board, a little extra chlorine in the tank won't hurt (provided it's not a crazy amount) as it'll be significantly reduced by the filters before reaching the tap (we filter all of our onboard water, not just for drinking).

[wingssail]

Originally Posted by Jammer

I think your approach is sound, but, regarding water borne illnesses, how would you know? 38 years without a single bout of diarrhea?

Well now, I didn't say that. Even though we drink watermaker water (which has not been passed through either the tank or filter, but directly into bottles) we've had bouts periodically. Salad in a local restaurant is a good source of bug. Serious problems? No.

And when in Asia it seemed like everyone had bouts a couple of times a month, including locals. At a restaurant last night with a large party, half of the people were mentioning recent problems, yet all drink bottled water (or beer) and we all concluded, "You never know where it came from unless five people ate the same thing and all get sick".

And by the way, tap water everywhere can have problems, even in western countries.

[sv_pelagia]

Ensenada water is a special case: water there has a very high salinity, so filtering doesn't help. But yes, very easy to have locals bring in 5-gallon (if I recall correctly, actually 19 litres) "garafon" bottles to fill your tanks. (We did this also innMazatlan.)

In most other places, we filtered AND chemically treated dock water. Your UV & filter setup sounds great. If not using combo of filter & chemical (or filter & UV), filter must be <1 micron. Filter alone cannot deal with viruses.

https://www.cdc.gov/healthywater/dri...treatment.html

We didn't have a water maker and it wasn't a problem to get water.

[ejs]

We found the marina water in Mexico came in three types when you asked.
1"we have our own on-site RO plant and the water is tested and completely safe". 2 "We drink the water every day but you might not be used to the bugs in it so buy bottled water"
3 "no one drinks this water, it is only good for boat washing"

One marina we stayed on the Baja had a water truck that went once a week up to a lake, filled up , and brought it down and pumped into the marina cistern. Type 3 and they told you so