Good day to all, We recently sailed south to Mexico and are going to continue further south for some time to come. I noticed that a few of the cruising boats that we saw at a local marina had what looked like a standard sediment filter hooked up to the dock hose and were using this to fill their water tanks for use as drinking water. Years ago I had read that the tap water in Mexico should be considered suspect due to parasites that when ingested are the primary cause of the infamous "Montezumas revenge". One of the individuals that I spoke to who had just started using his filter indicated that he had substituted a 2 micron filter for the 10 micron filter that came with the unit and as of that time had not had any issues. I am not up on my biology and if anyione out there knows whether a 2 micron filter will eliminate the contaminants or if my assumptions are wrong please advise and educate.
Filtering questionable water for drinking abroad
- Thread starter Alex 2740
- Start date
- Status
filtering for giardia
Not sure whether this was posted in 2005 or earlier. The CDC recommends a 1 micron filter for giardia and cryptosporidium. Also, this will NOT take care of viruses for the most part. You also need to disinfect. When in Mexico I fill my Pearsons's tanks water at the dock and use it for washing dishes and bodies. But use bottled water to drink. I am a water engineer. If you want more information email me at cpntodd@comcast.net
Not sure whether this was posted in 2005 or earlier. The CDC recommends a 1 micron filter for giardia and cryptosporidium. Also, this will NOT take care of viruses for the most part. You also need to disinfect. When in Mexico I fill my Pearsons's tanks water at the dock and use it for washing dishes and bodies. But use bottled water to drink. I am a water engineer. If you want more information email me at cpntodd@comcast.net
No 2uM is unsuitable
Giardia and Cryptosporidim and other similar cysts/parasites need 1 micrometer (micron) "absolute" filtration. Absolute means that the filtration media is *validated* to retain ~100% of the organisms (at 1uM size) that are in the fluid. A simple 1 micron filter (unless validated) cannot do this ... must be 'certified' or *validated* as 'absolute' for the retention size. For bacterial retention 0,2µM (or 0,1µM) is required, for viruses much much smaller and requires filtration below what a simple cartridge filter can do. These are not filters that a 'consumer' is able to install with any confidence that he/she will not contaminate the delivery system. Just because a filter has a such and such retention does NOT mean that the system will operate to that level of retention. Typically below 3-5 uM there is a requirement for 'piston seal o-rings' on the filter assembly or one risks organisms bypassing the filter though and by the 'end cap' seals. Any 'filter cartridge' used for biological blocking should be one with double (222 or 226) O-ring seals built-in the 'end-cap' of the filter .... and these a definitely not availble from sources such a HomeDepot or the WestMarine catalogue. It is damn difficult to change such a filter without contaminating the 'downstream' piping .... any change-out needs to be followed with shock sanitization by various appropriate chemicals and very careful 'technique' to make such a change. Giardia and Cryptosporidium are totally unaffected by chlorine/chlorox disinfection/sanitization methods. Any filter is better than no filter but at this small retention level, one needs a certain amount of knowledge and change-out 'technique' so as not to contaminate the system .... as filter membranes 'concentrates' the organisms on the filter surface. One or two 'escapees' that get downstream when you change a cartridge can/will rapidly 'divide' into new colonies and contaminate what you 'think' you are protecting. Im deeply involved in 'filtration engineering' ... and I carry jug water for drinking.
Giardia and Cryptosporidim and other similar cysts/parasites need 1 micrometer (micron) "absolute" filtration. Absolute means that the filtration media is *validated* to retain ~100% of the organisms (at 1uM size) that are in the fluid. A simple 1 micron filter (unless validated) cannot do this ... must be 'certified' or *validated* as 'absolute' for the retention size. For bacterial retention 0,2µM (or 0,1µM) is required, for viruses much much smaller and requires filtration below what a simple cartridge filter can do. These are not filters that a 'consumer' is able to install with any confidence that he/she will not contaminate the delivery system. Just because a filter has a such and such retention does NOT mean that the system will operate to that level of retention. Typically below 3-5 uM there is a requirement for 'piston seal o-rings' on the filter assembly or one risks organisms bypassing the filter though and by the 'end cap' seals. Any 'filter cartridge' used for biological blocking should be one with double (222 or 226) O-ring seals built-in the 'end-cap' of the filter .... and these a definitely not availble from sources such a HomeDepot or the WestMarine catalogue. It is damn difficult to change such a filter without contaminating the 'downstream' piping .... any change-out needs to be followed with shock sanitization by various appropriate chemicals and very careful 'technique' to make such a change. Giardia and Cryptosporidium are totally unaffected by chlorine/chlorox disinfection/sanitization methods. Any filter is better than no filter but at this small retention level, one needs a certain amount of knowledge and change-out 'technique' so as not to contaminate the system .... as filter membranes 'concentrates' the organisms on the filter surface. One or two 'escapees' that get downstream when you change a cartridge can/will rapidly 'divide' into new colonies and contaminate what you 'think' you are protecting. Im deeply involved in 'filtration engineering' ... and I carry jug water for drinking.
Thanks and a lttle more info
Thanks to Rich Todd and Ross for your help. Very educational and I am sure I will use it all in the future. The secondary reason that issue came up for me is that until now (as Ross suggested) I have been using a chlorine additive to the water that I have used from the dock to fill the tank and that has seemed to work quite well so far. I have a R/O watermaker on board and it clogged while underway so I needed to flush the system and membrane in order to get the unit to work. To do so, un-chlorinated, unsalted, source water must be used to avoid damging the R/O membrane. The water in my tank was certainly drinkable but not usable to recommision the watermaker. Perhaps it would be easier to just have a carbon filte rof some sort that can filter out the chlorine from any water that I use for Watermaker maintenance. If you have any feedback on the efficacey of Chlorine in this application or other suggestions please feel free to post or contact me directly at alopez865@earthlink.net.
Thanks to Rich Todd and Ross for your help. Very educational and I am sure I will use it all in the future. The secondary reason that issue came up for me is that until now (as Ross suggested) I have been using a chlorine additive to the water that I have used from the dock to fill the tank and that has seemed to work quite well so far. I have a R/O watermaker on board and it clogged while underway so I needed to flush the system and membrane in order to get the unit to work. To do so, un-chlorinated, unsalted, source water must be used to avoid damging the R/O membrane. The water in my tank was certainly drinkable but not usable to recommision the watermaker. Perhaps it would be easier to just have a carbon filte rof some sort that can filter out the chlorine from any water that I use for Watermaker maintenance. If you have any feedback on the efficacey of Chlorine in this application or other suggestions please feel free to post or contact me directly at alopez865@earthlink.net.
- Status