Cleaning Freshwater Tanks

[moe_1200]

Is there a recommended procedure for conducting a thorough cleaning of freshwater holding tanks? I have (2) freshwater tanks, 1 in the v-berth and another on the under the starboard settee. The boat was in storage for 6 years, it was winterized but developed quite a bit of mold, mildew and scum in the tanks & lines (I don't think they were in great shape prior to storage already).

I'm going through and replacing all of the freshwater hoses but I don't think a chlorine soak of the tanks is going to be sufficient to get them clean. I don't need to get them to drinking water quality but I'd like to be good enough to use them for washing, cooking, etc.

For drinking water I've removed the hot water heater (was already inop.) located in the port lazarette and will be using that space to install a 5 gallon water tank (think water cooler tanks) connected to a small 12v diaphragm pump with a faucet/switch at the sink. This will be used solely for drinking water and can be swapped out easily once empty.

 

[Don S/V ILLusion]

There are all kinds of recipes for disinfecting potable water. And tanks. The same problem always remains - you don’t know what you don’t know. Absent a visual inspection and physical cleaning of the tank walls, you can’t be certain what’s growing there. Simply testing the water at the tap isn’t an indicator of anything except the moment at which the sample is taken.
If you aren’t going to use the tank water for consumption, no problem. If you change your mind, install inspection/access ports in the tanks.

 

[kappykaplan]

See this post for a start:

Water tank cleaning

I have a 2003 Bavaria 36. The bow water t ank was not maintained by the previous owner and has a significant scum ring around the perimeter of the tank. There's no way to reach the surface in most parts of the tank. Is there any treatment that will dissolve the scum buildup? Thanks in advance.

forums.sailboatowners.com

 

[moe_1200]

There are all kinds of recipes for disinfecting potable water. And tanks. The same problem always remains - you don’t know what you don’t know. Absent a visual inspection and physical cleaning of the tank walls, you can’t be certain what’s growing there. Simply testing the water at the tap isn’t an indicator of anything except the moment at which the sample is taken.
If you aren’t going to use the tank water for consumption, no problem. If you change your mind, install inspection/access ports in the tanks.

The tanks already have an inspection port on them. That’s how I figured out how bad of shape they were in. I was thinking of getting some type of 90 degree bent adapter for my pressure wash to try and spray around inside the tank. Dislodge some of the gunk and pump it out. Then once that’s done put in some bleach solution.

 

[mermike]

Peggie Hall's book, and Practical Sailor both have excellent information on tank maintenance.

 

[dlochner]

The tanks already have an inspection port on them. That’s how I figured out how bad of shape they were in. I was thinking of getting some type of 90 degree bent adapter for my pressure wash to try and spray around inside the tank. Dislodge some of the gunk and pump it out. Then once that’s done put in some bleach solution.

Amazon has a number of fittings for pressure washers that allow you to get into difficult places. We used that on our tanks with good results.

In the future do not put antifreeze in the tanks, it is simply food for all kinds of bad stuff.

We used a dedicated potable water hose and an RV filter when filling the tank and use a Brita filter for all drinking water. So far, no problems and the water tastes good.

 

[Don S/V ILLusion]

The tanks already have an inspection port on them. That’s how I figured out how bad of shape they were in. I was thinking of getting some type of 90 degree bent adapter for my pressure wash to try and spray around inside the tank. Dislodge some of the gunk and pump it out. Then once that’s done put in some bleach solution.

Good start but make sure you remove the “gunk” the pressure wash dislodges. Any residual stuff will serve to promote further growth. Pressure washing moves it around well but doesn’t remove it all. Just another fun boat project.

 

[moe_1200]

Amazon has a number of fittings for pressure washers that allow you to get into difficult places. We used that on our tanks with good results.

In the future do not put antifreeze in the tanks, it is simply food for all kinds of bad stuff.

We used a dedicated potable water hose and an RV filter when filling the tank and use a Brita filter for all drinking water. So far, no problems and the water tastes good.

Thanks, I was actually looking at the different fittings on Amazon. Glad to see someone else tried this and it seemed to work.

Pre-filtering before filling the tanks is probably a good idea. I'm probably overthinking it but an inline UV filter might help when filling tanks. I'd already be connected to shore power when filling up so electricity to the UV wouldn't be an issue, maybe just an extra layer of protection to keep the bacteria out. Of course that's only if I can get the tanks clean enough to start...