Algae in freshwater system filter possibly seen in watermaker 5 micron filter

[autumnbreeze27]

I've got a standard water filter on my freshwater system, the water goes from the tank to the filter, from the filter to the pump, from the pump to an accumulator tank. Everything but the hose and tanks are 6-12 months old.

My watermaker was plumbed so that the water came from the ocean, through a sea strainer, then a 20 micron filter, then there is a valve where I can put fresh water or the 20 micron filtered salt water to the unit, which had a 5 micron before the pump.

My intention was to relocate the 5 micron filter to put it next to the 20 micron for easier servicing (and not getting salt water all over the motor/pump/etc since it's all together).

When I pulled the 5 micron unit out it had large flakes of green stuff in it. I call it algae but I may be mistaken. I usually see the same crap in my freshwater filter. So I pulled the fresh water filter and sure enough it had some of the same stuff in it.

I had last replaced the freshwater filter 2 months ago, and was scheduled to replace it next month. I have regularly seen these green flakes as well as algae growing on the filter in the past. Right before we left to go cruising I cleaned the freshwater filter with bleach, and inspected both tanks but the water in the tanks is clean (as are the tanks, both stainless steel).

Normally I use the watermaker every 1-3 days without flushing it. When in a marina I flush it with fresh water, and wash the filters and dry them in the sun for UV cleaning.

So here's my questions:
1) I assume the green flakes in the 5 micron filter housing were from my freshwater? The flakes were fairly large, unless they grow in there I don't see how they could have gotten past the 20 micron coming from the ocean. I didn't take a picture but they were the size of fish food (for aquariums, larger pieces)
2) I decided to move the freshwater flush valve for the watermaker to in front of the 20 micron filter, so when I flush it will remove the saltwater from both filters, as well as filter the fresh water in case any of this algae is getting past the primary water filter.
3) Is it normal to get algae in the water filter housing? Should I be cleaning this once a month? Should I be adding bleach to my water tanks? One tank is plumbed to the water maker, the other is not. When I load up with marina water I filter it with carbon so any chlorine is removed. The primary water filter is carbon as well. It blows through a lot of water when I re-prime the filter and remove all the air from the system, so I would only do it with a marina where I could refill the tanks before heading out.

[SV THIRD DAY]

It's quite common for algae to grow in your fresh water tanks and plumbing. If we did not bleach our tanks at least once every 6 months, no matter how good our RO Water was coming out of the water maker, once it went into the SS tank it tasted like a "Pond" according to my wife. Just putting an AC filter on the galley sink didn't help the taste/smell in the shower or heads. So we did the 1/4 cup of bleach per 50 gallons of water trick and it kept them clean.

CAUTION: of course you can't fresh water flush your water maker after you bleach your tanks for a least two weeks to allow for off gassing of the chlorine and I would never fresh water flush the water maker without a Fresh AC filter (Fresh being no more than 6 months old).

For your water maker loop, if you are not fresh water flushing after each run then you are setting up the environment in your prefitlers and plumbing (and RO Membranes) for algae to flourish in the warm happy environment.

[Lepke]

SV 3rd Day has it right. Tanks will always grow something. The contamination can come from air carried into the FW tank vent when water is used. I only us RO water, but still have to bleach my tanks. Since I'm in a cold climate, not as often as Morro Bay.
On ships, the engineers monitor the FW and add chemistry as needed. On boats, we have a small version of ships tanks and have to monitor them ourselves. While I don't like chlorine, I use a pool chlorinator kit and shoot for the bottom of the scale to maintain a level below where it can be tasted.

[autumnbreeze27]

I'll have to keep an eye out for the pool tester strips... I've got a pH tester but I'm pretty sure that won't test for chlorine.

I added a shot glass of bleach to each tank. Seems to have helped take the swampyness out.

Is there any way to test the effectiveness of the charcoal in the fresh water filter? I'm scared I'll hurt my membranes. I'm using home depot GE filters and they say replace every 3 mo, I'm at 2 mo on it.

We used to fill the boat with long beach water, and we'd probably drain and refill a tank a week or so. We softened the water but didn't remove chlorine until the filter before the fresh water pump. Now that we're cruising when we filter the dock water it's got charcoal there so I'm guessing the flavor is from the RO water or filtered dock water not having ANY chlorine in it.

Thanks for the info. We'd still get slimy filters when we were living in the marina in LB, but when I inspected the tanks they were always clean.

[SV THIRD DAY]

Please be careful...
The AC paper filters impregnated with AC dust are horrible to use in water makers, just don't have a high Cl loading and they require pretty low flow rates to remove Chlorine properly. As a water maker manufacturer, I would strongly recommend only using AC Carbon block filters that have a better Cl capture and loading rates. You can get good quality AC ock filters for like $9 online and then change them out at minimum every 6 months. Remember Cl damage can be a "one and done" membrane failure event.

[autumnbreeze27]

I googled the filters I have and they are Carbon Spun Fiber. They say they last up to 3 months or 15k gallons, I'm no where near the 15k gallon mark.

So I'll replace them every 2 months instead until they're used up.

I got a couple of 1 or 2 micron carbon block filters from Tom for my dockside water filter setup I made... should I use these same filters for my freshwater system?

[SV THIRD DAY]

Originally Posted by autumnbreeze27

I got a couple of 1 or 2 micron carbon block filters from Tom for my dockside water filter setup I made... should I use these same filters for my freshwater system?

Yes the Carbon block filters are much better. It's not the total gallonage your care about as much as the flow through rate and % removal.