What's this stuff in my water tank?

peaman

Member I
So today, I cut an opening in two of my water tanks to install a cleaning and inspection port. I was disgusted by what I found inside and am glad I will have inspection ports now.

Any idea what the stuff is that's in my tanks? and best way to prevent it? I just bought the boat, so I don't really know the history of the tanks. (the white crumbs are from cutting the opening.)
 

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gabriel

Member III
Probably algae that forms from letting water sit in the tank. The solution would be to drain when not in use and rinse with a bleach solution or something similar that would disinfect the tank.
 

Frank Langer

1984 Ericson 30+, Nanaimo, BC
Peggy Hall (and others) have written quite alot about how to keep both water tanks and holding tanks clean and odour free. You may want to search a bit, as there is lots of good guidance. Some people also install a water filter in their water line between the tank and the water faucet, but that's only effective if you clean it or add charcoal as a regular maintenance item.
Frank
 

toddster

Curator of Broken Parts
Blogs Author
That is dried-up biofilm. It’s in the pipes in your house too, but you can’t see it, so you don’t worry about it. Clean out the system as best you can. Maintain residual chlorine as per WHO guidelines. 8 drops of household bleach per gallon. For my tanks, that works out to a capful per fill. Avoid filters unless you suspect chemical contamination - they are excellent habitat for bacteria and have a zillion times the surface area = a zillion times the biofilm. (“Test” results on the label are only valid for a few hours after installation.) I did make a Baja filter for water similar to the one described in Practical Sailor for filling tanks, but that’s just to remove gross contamination. (My marina is plumbed with white PVC pipe - they couldn’t make a better system for growing black algae if they tried.)
 

peaman

Member I
Thanks for an excellently detailed response, toddster!

The tanks cleaned up pretty well with minor scrubbing using a bit of dish detergent and bleach. And with my new clear inspection ports, I'll be able to keep an eye on them.
 

nquigley

Sustaining Member
Thanks for an excellently detailed response, toddster!

The tanks cleaned up pretty well with minor scrubbing using a bit of dish detergent and bleach. And with my new clear inspection ports, I'll be able to keep an eye on them.
I'm really keen to add these ports - not so keen to see what's inside my tanks though.
What size of (clear) inspection ports did you get? (i.e, what hole size did you cut?)
Did you install one or two ports per tank?
What part number did you order, and from where?
Can you reach all corners of the tank from the port(s).
 

peaman

Member I
Got a photo of the inspection port you used on the plastic tank?
This is a 6" deck plate, Beckson DP-W-C from Defender, installed in a 6-1/4" opening and bedded with recommended silicone sealant. My tanks are not big, largest dimension of 36" in the stbd tank, so only one access per tank. I can reach all corners of the tank by hand (I'm not a big guy).

I will cut a smaller, 2" opening in the covering board on the port and stbd tanks so I'll be able to glance inside by just lifting a cushion. That's not required on the forward tank, since that tank is separetly secured and the covering board is not screwed down.
 

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