Inexpensive Watermaker pre-filters

[LifesBetterWhenYoureBeating]

The manual for my spectra Catalina says I should only use spectra pre filters, but those are expensive and not easy to find so I'm looking for alternatives. Would these polypropylene filters do the job without any risk of damaging my membrane?
https://www.amazon.com/gp/aw/d/B082PB9JMJ

If not, are there any others out there that don't cost $20 a pop?

Thanks in advance!

[markxengineerin]

I happened to just order these, but can't comment on how good they are yet

[PNWSalmon]

The spectra pump uses check valves in its process. Cheap paper filters can tear and block these check valves, causing system malfunction and costly and/or time-consuming repair. My understanding of the system is that you can take many shortcuts, buy non-spectra membranes, use whatever parts you want, but you shouldn’t use cheap pre-filters.

[Avionics_Joe]

Originally Posted by LifesBetterWhenYoureBeating

The manual for my spectra Catalina says I should only use spectra pre filters, but those are expensive and not easy to find so I'm looking for alternatives. Would these polypropylene filters do the job without any risk of damaging my membrane?
https://www.amazon.com/gp/aw/d/B082PB9JMJ

If not, are there any others out there that don't cost $20 a pop?

Thanks in advance!

This is what I use, as I was in a high algae area I got a lot. Now in the Bahamas I only need one every 4 months not every 4 weeks. You do want a 5 Micron filter to protect the membrane.

[davil]

Originally Posted by markxengineerin

I happened to just order these, but can't comment on how good they are yet

==========================

just a tip

when cruising I will change the filters quite often, the used one will tie to a line and trail it for a while, then will bring them aboard and dry them out in the cockpit

That avoids damaging the inside of the pleats and cleans the sediment that tends to accumulate.

will rotate them and get quite an extra use.

[Tellie]

Originally Posted by davil

==========================

just a tip

when cruising I will change the filters quite often, the used one will tie to a line and trail it for a while, then will bring them aboard and dry them out in the cockpit

That avoids damaging the inside of the pleats and cleans the sediment that tends to accumulate.

will rotate them and get quite an extra use.

With all due respect. DO NOT drag filters behind your boat. I learned this the hard way when I used to recommend dragging them behind a boat as well. It is a filter, it will still filter things when you are dragging it behind your boat. If you put a line through the filter with a safety knot as many do then you are reversing the flow of the filter and then filter is now filtering in the wrong direction. Once you re-install this filter the flows are reversed again and any filtered material on the wrong side of the filter will now be released into your system and membrane/s at a much larger size than five Micron which is the size we need to filter down to so debris will not get stuck in the membrane/s. My hard lesson here was four membrane replacements on a watermaker withing two months. A small flying fish was caught on the inside of a filter dragged and when re-installed flooded the system with emulsified fish parts. Once we finally figured all this out, this is why we never recommend dragging filters.

[Tellie]

Originally Posted by PNWSalmon

The spectra pump uses check valves in its process. Cheap paper filters can tear and block these check valves, causing system malfunction and costly and/or time-consuming repair. My understanding of the system is that you can take many shortcuts, buy non-spectra membranes, use whatever parts you want, but you shouldn’t use cheap pre-filters.

This is correct. Though any watermakers high pressure pumps can suffer from cheap filters the membrane as well is now the filter for remnants of cheap filters and the membrane will not pass these remnants through but collect them in the input of the membrane where it will eventually clog it to the point of replacement of a membrane that would and should have lasted a lot longer.

I learned this lesson years ago when I was a teenager riding motorcycles. My first bike and the man behind the counter said, if you have a $10 head buy a $10 helmet. So, in conclusion, if you have a cheap watermaker, buy cheap filters.

[LifesBetterWhenYoureBeating]

Originally Posted by Tellie

This is correct. Though any watermakers high pressure pumps can suffer from cheap filters the membrane as well is now the filter for remnants of cheap filters and the membrane will not pass these remnants through but collect them in the input of the membrane where it will eventually clog it to the point of replacement of a membrane that would and should have lasted a lot longer.



I learned this lesson years ago when I was a teenager riding motorcycles. My first bike and the man behind the counter said, if you have a $10 head buy a $10 helmet. So, in conclusion, if you have a cheap watermaker, buy cheap filters.

Ok, I'm sure most cheap filters will be low quality and could end up damaging my wm but I don't want to use price as the sole judging criteria when selecting filters so I'd really appreciate if you could tell me other characteristics to look for. For instance, what material is preferable: polypropylene, cellulose polyester, or something else?

Or do you think that it is better to just stick to specific brands? If so, which ones do you recommend?

[markxengineerin]

Here are what the ones in my order above look like for <$5 each



Would someone with expensive filters be able to see if they look the same?

I have not seen if these are salt water rated, hopefully they are.

[Tellie]

They are the pleated polyester filters like the ones shown above. Even in these filters quality is all over the place. The less expensive ones use thinner material and less of it so you'll go through those faster than the higher quality ones. You'll also get more multiple uses out of a better-quality filter. So, for the most part you really don't save all that much going cheaper. The reason to go better quality is just that, you have a very expensive investment in your watermaker. No filter is 100% perfect and all of them will eventually let something by that can't pass through the membrane. The better-quality ones are just more resistant to that than cheap filters.

[markxengineerin]

Thanks, i'll cut one of these open and get the expensive ones next time to compare.

A couple other random thoughts/questions:

My screen strainer rusts, so I'm thinking of just pulling the screen out permanently. The 1st pre-filter never clogs and per the advice of this thread, I'm taking them out to clean after every single use. Anything the strainer would have caught will easily be caught by the 1st pre-filter then hosed off the same day. Any reason not to do this?

The rust is probably filtered out, but it's not appetizing to think of it in the drinking water. I know the stainless fittings are probably doing the same thing, but at least I can't see them : )

For membranes, why is it that they shouldn't be stored dry, but the pre-filters should be? I've been going 2 weeks in between uses with just a fresh water flush each time, no signs of trouble yet, but I'd like to be able to push that number higher. Wish there was a cheaper and easier way than the periodic flushing or Z-ion.

[PNWSalmon]

Originally Posted by markxengineerin

Thanks, i'll cut one of these open and get the expensive ones next time to compare.

A couple other random thoughts/questions:

My screen strainer rusts, so I'm thinking of just pulling the screen out permanently. The 1st pre-filter never clogs and per the advice of this thread, I'm taking them out to clean after every single use. Anything the strainer would have caught will easily be caught by the 1st pre-filter then hosed off the same day. Any reason not to do this?

The rust is probably filtered out, but it's not appetizing to think of it in the drinking water. I know the stainless fittings are probably doing the same thing, but at least I can't see them : )

For membranes, why is it that they shouldn't be stored dry, but the pre-filters should be? I've been going 2 weeks in between uses with just a fresh water flush each time, no signs of trouble yet, but I'd like to be able to push that number higher. Wish there was a cheaper and easier way than the periodic flushing or Z-ion.

The rusty Monel seems unusual. You should get one that is a higher grade, and more resistant to salt water. Where do you cruiser, is the salinity higher ?

Getting rid of the mesh filter is a bad idea. We have sucked in jelly fish before, and it’s was a big old mess. The mesh filter saved a ton of cleanup. Multi-stage filter through a series of finer filters exists to make your life easier.

As to dry pre-filter versus membrane, is because the membrane is just that
, a membrane, not a filter. The watermaker is using high pressure to rush water past the membrane and create a high and low pressure side that allows the effects of osmosis to occur. You are not filtering out saltwater, you are using osmosis.

The pre-filter just thst, a filter, it just catches stuff bigger than 5 microns. Then it clogs and that’s it. If it dries out, it will just get wet again and do it’s thing. When a membrane dries or or clogs you are losing the properties that allow it to work. So anyways osmosis versus filtering, different things. There’s a good podcast on reverse osmosis and lots of good articles that get more scientific and accurate than my piss poor explanation, but I hope I set you off on the right track anyway

[Tellie]

Originally Posted by markxengineerin

Thanks, i'll cut one of these open and get the expensive ones next time to compare.

A couple other random thoughts/questions:

My screen strainer rusts, so I'm thinking of just pulling the screen out permanently. The 1st pre-filter never clogs and per the advice of this thread, I'm taking them out to clean after every single use. Anything the strainer would have caught will easily be caught by the 1st pre-filter then hosed off the same day. Any reason not to do this?

The rust is probably filtered out, but it's not appetizing to think of it in the drinking water. I know the stainless fittings are probably doing the same thing, but at least I can't see them : )

For membranes, why is it that they shouldn't be stored dry, but the pre-filters should be? I've been going 2 weeks in between uses with just a fresh water flush each time, no signs of trouble yet, but I'd like to be able to push that number higher. Wish there was a cheaper and easier way than the periodic flushing or Z-ion.

It's the nature of the maintenance beast when it comes to watermakers.

[Bill O]

Tellie,
Are the spun pre-filters any better? With some of the spun ones you can remove a few of the windings to get a fresh surface to extent the life. (inspected these after this process and the filter isn't permeated past ~ 2 layers of windings)

[Tellie]

Hi Bill,
I'm not a fan of either the spun or the wound filters. These two types of filters have a tendency to give off very small fibers that can clog the input to the membrane itself. You can "pinch" either filter and easily pull off some material. Anything you can visually see from the pinch will not pass through the membrane and slowly begin the clogging process. The longer and older these types of filters remain in the watermaker the more they eventually start to give off. Does it mean that every membrane will be impacted by every spun filter? No, but this is certainly one of those precautionary Oz. of prevention things.