Keeping algae out of fresh water tanks

[crieders]

Now that I have cleaned he fresh water  tanks, filters and got rid of the algae, whats the best preventative for reoccurance

[Ted Pounds]

Add a few capfuls of bleach with every fill-up.   

[Jon Schneider]

And if you don't usually use both tanks on one trip, then only keep the forward tank filled, and leave the aft tank dry (weight distribution benefit to this strategy as well).

[Mike and Joanne Stimmler]

I think there was a write up that said not to add routine bleach to your tanks because the small amount (a few capfulls) does not help much and that the chlorine dissipates rather quickly leaving a byproduct of the chlorine (I don't recall what the byproduct is called but perhaps Ron or Stu knows or remembers) that can cause problems.

The best way is to USE the water in your tanks, switching between the two tanks so that the water is changed and flushed on a routine basis.

THEN, yearly you should do the high dose bleach flush as it sounds like you just did.

Also, when I add water to my tanks I have a special hose reserved for just that, made for providing drinking water and I also use a carbon filter, which I purchased from Home Depot with hose adaptors on each end (the type of filters used for whole house filters with replaceable cartridges).


It is also best to fill the tanks after washing the boat so as to flush out the water lines at the marina

Hope this helps    
Mike

[crieders]

I tried the few capfuls of bleach last season and it did not help at all. I don't use the water completely since we do a lot of day sailing. Perhaps the best idea is to keep the tanks empty except on  trips. Of course, its nice to have some fresh water available

[Ken Juul]

It sounds like you should only use the forward or smaller tank.  If you fill with "city" water it should have enough chemicals to keep the water clear.  Using the water is the key. 

At my marina we have well water.  First trip of the season is up the river to good city water.  After that it's bring 5 or 10 gals of water from the house to the boat every weekend.  We use more than that on a weekend so the tank level gradually decreases necessating a trip to an other marina with city water at some point during the summer.  Using and replacing the water is the key to keep it fresh.

[Ron Hill]

Cliff : Most cruisers will agree that "you can't save water" - you've got to use it.  As mentioned you need a cap full of bleach in the starboard tank and two cap fulls in the aft tank.  If you are using "city" water then adjust accordingly with less bleach. 
The key is to use water and keep it moving!  I always use out of the starboard tank and then transfer from the aft tank to refill the starboard (thru gravity).  Then I refill and filter the water going into the aft tank. 
Jon has a point that if you're only a short weekender trip you may want to only carry water in the starboard tank.  However, I leave port with all tanks full - just in case I get stuck - recalling the saying from the Old Mariner --- "Water water everywhere and not a drop to drink".

You can always drain all tanks at the dock and refill!!   A thought 

[Stu Jackson]

Cliff, go to www.catalinaowenrs.com and type in "recommission" in the archive search box.  You will find Peggie Hall's discussion of what the correct way to do it is.  We used to have some of this material of hers on our site, but we removed it when she published her book.

[Roc]

Per P. Hall's freshwater commissioning, here's what I do.  Pour one cup bleach per 10 gallons of water into the tank.  25 gallon tank, 2-1/2 cups of bleach for a full tank.  Run every faucet, both hot and cold, until there is a strong smell of bleach.  Once you've done that, keep the system pressurized (keep water pump breaker on) for at least 8 hours, but not more than 24 hours.  Then, purge, fill, purge fill each tank.  I purge each tank 3 times.  Remember to let the dock water run for 15-20 minutes through your hose before purging the bleach out of the tank.  What I do is wash my boat first, then I know the water lines are pretty clean (water sitting in dock piping in hot sun can introduce critters back into your tanks).  I follow this procedure every spring and have no issues with algae, off odor, etc.