Changing WM filters

[monte]

I just changed the WM filter and curious as to what others use and change frequency etc.
Our WM is a aqua base 65l/h dc unit and uses 24A when running. It runs to spec and production is around 200-300ppm solids.
We run it for about 3 hrs, twice a week and have been doing that for the past year. We always freshwater flush afterwards. We've changed the filter 3 times, so around every three months. We try to run it only in clear water.
We have been using a cheapish polypropylene filter bought on eBay for a few bucks each. The first filter that came with the unit was a woven type. Both types are 5 micron and the only other filtration is the seawater strainer and a carbon filter on the flush inlet side which we haven't
replaced as we don't flush with town water.
Although the old filters look a bit mangy, there's no bad smell and water produced is fresh and under 300ppm, so I'm rinsing and drying the old ones for re use if need be.
We drink the water every day and no ones died yet.
So what's others preferences for filters, woven or poly? Changing periods or reasons for changing?comments...

[Tellie]

Originally Posted by monte

I just changed the WM filter and curious as to what others use and change frequency etc.
Our WM is a aqua base 65l/h dc unit and uses 24A when running. It runs to spec and production is around 200-300ppm solids.
We run it for about 3 hrs, twice a week and have been doing that for the past year. We always freshwater flush afterwards. We've changed the filter 3 times, so around every three months. We try to run it only in clear water.
We have been using a cheapish polypropylene filter bought on eBay for a few bucks each. The first filter that came with the unit was a woven type. Both types are 5 micron and the only other filtration is the seawater strainer and a carbon filter on the flush inlet side which we haven't
replaced as we don't flush with town water.
Although the old filters look a bit mangy, there's no bad smell and water produced is fresh and under 300ppm, so I'm rinsing and drying the old ones for re use if need be.
We drink the water every day and no ones died yet.
So what's others preferences for filters, woven or poly? Changing periods or reasons for changing?comments...Attachment 103403Attachment 103404

The word "cheap" always throws me a bit. There's no relation to the pre-filter and the ppm readings. The pre-filters are there to protect the system from undue wear and to protect the membrane from pre-mature fouling. A five micron pre-filter by itself won't stop anything that will kill you from getting through, that's the membranes job. I don't like anything but pleated filters in a watermaker. String wound or spun type filters give off small bits of material that can easily find their way into the input side of the membrane and slowly block the free flow of the membrane. These filters are fine for under the sink at your house, but not for a boat based watermaker. I would still change out the charcoal filter every six months regardless if you only use watermaker water to flush with. If the fresh water is coming from your tanks it needs to be filtered as well. Fresh water tanks that only see RO water are far more likely to see more growth and nasties in the tank itself. It's a good idea to every now and then to fill your tanks with good dock water. The residual chlorine in residential water helps keep the growth down. RO water has no protective qualities. Let the charcoal filter do what it is intended to do.
How often you change the pre-filters varies all the time. It mainly depends on water condition not how many hours the watermaker runs for. If you run your system at a dock you may need to change the filter out in a few hours of run time. Offshore, where watermakers do best you will probably change them out once a month. Even if a water maker sits unused for two months and just fresh water flushes I would recommend changing them out every two months. The filters on any watermaker are the consumable items to a rather expensive item. Don't go cheap and change your filters often. You can buy a lot of good quality filters for the cost of one service/repair call from your watermaker tech.

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[monte]

Thanks Tellie great advice as always. So what filters would you recommend? Specific brand? Do marine stores like budget marine sell decent quality filters? We will be in grenada shortly so we can have some delivered from the US if need be, it's just a matter of what is recommended. As I mentioned, ours seem to be doing a good job but I definitely agree whatever is best for the WM is worthwhile paying a bit extra for. I've been thinking about flushing the system as well as you mentioned. I was going to add a chlorine tab or something but dock water sounds like an easy option. We are sure to visit a marina sometime over the coming months.
Cheers

[monte]

As far as keeping the tanks bug free, we usually run the tanks dry every few weeks to totally change the water. His seems to work but maybe a filter under the sink would be a good idea as well.

[Tetamanu]

Hi there,

Just recently build a watermaker in my boat with a prefilter of 5 micron
polyprop wounded. We are trying to get the poly pleated. I have been monitoring the seawater temp, flowrate and the ppm from start to end every time i run the watermaker.
I run the WM every other day for 1 hour which makes about 60 liters fresh water.
I have found that every time i make water the ppm value at the start as well as the ppm value at the end goes up roughly 20 ppm.
So i start with a fresh filter which gives me 180 ppm at start and 160 ppm at the end, the next is 200 at start and 180 at the end.
Now i change the filter every week and try to wash them by towing them behind the boat on a line.
After trying it on a new run it gives 250 ppm start and 230 at the end.
I flush the system with the first 10 liters i make.

Now for the questions:

Do you use anything like the pickeling stuff to clean the prefilters.
What is a reasonable ppm value to change the filter.

thanks for your time

[Tellie]

Originally Posted by Tetamanu

Hi there,

Just recently build a watermaker in my boat with a prefilter of 5 micron
polyprop wounded. We are trying to get the poly pleated. I have been monitoring the seawater temp, flowrate and the ppm from start to end every time i run the watermaker.
I run the WM every other day for 1 hour which makes about 60 liters fresh water.
I have found that every time i make water the ppm value at the start as well as the ppm value at the end goes up roughly 20 ppm.
So i start with a fresh filter which gives me 180 ppm at start and 160 ppm at the end, the next is 200 at start and 180 at the end.
Now i change the filter every week and try to wash them by towing them behind the boat on a line.
After trying it on a new run it gives 250 ppm start and 230 at the end.
I flush the system with the first 10 liters i make.

Now for the questions:

Do you use anything like the pickeling stuff to clean the prefilters.
What is a reasonable ppm value to change the filter.

thanks for your time

Pre-filters are the consumable part of any watermaker. The only real cleaning you can do is a gentle rinse. Bleaching or scrubbing only damages a pre-filter which will more than likely make your 5 Micron pre-filters a 100 Micron filter and useless. That being said, I personally don't like the polyprop wounded filters. Many people and some watermaker companies sell them. I avoid them like the plague. First they just don't flow as well as a pleated filter will and cheap wound filters tend to give off very fine threads that find their way into the input side of your membrane permanently clogging the membrane until eventually the membrane is not nearly as effective as it could be. PPM readings varying 20ppm is an infinitesimal amount as to not even be a concern on a boat based watermaker. Temperature and salinity of the water around you can easily make that much difference even at anchor. It is not at all unusual for a system to produce a better ppm reading after it has been run for awhile. But a one hour run time in my experience is too short of a run time. Even Spectra recommends a one hour run time. I say a two hour run time is better for the membrane as it gives a far better flush action across the membrane (this also may be why you experience a better ppm reading at the end of your run time) Also, if you are changing your filters every week with only a one hour run time every other day then you certainly want to use a good pleated filter or maybe you might be more concerned of the area you are operating your system in. Using a storage solution or a pickling chemical is not recommended to clean pre-filters. Buy enough spares that when they are too dirty to clean by a gentle rinsing, or become too spongy, that you simply replace them. Even a DIY watermaker is not cheap to build. Again, the pre-filter is the consumable item that protects your investment. Buy enough and throw them away when they lose their effectiveness to protect your system. Best Regards J.T.

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