Water tank maintenance

I have seen Peggie Halls post on shocking water tanks. What I am not sure about is the amount bleach to be mixed in. I have a 144 gallon tank, am I correct in calculating a gallon of bleach? (Assuming 16 cups to a gallon).

This is an excerpt from Peggie Halls post on Trawler Forum:

1. Prepare a chlorine solution using one gallon of water and 1/2 cup (4
oz) Clorox or Purex household bleach (5-7% sodium Hypochlorine
solution). With tank empty, pour chlorine solution into tank. Use one
gallon of solution for each 5 gallons of tank capacity.

Also is doing a treatment with half a tank of water and taking the boat out for the day a good way to wash out the tank? Is there any downside to doing this? I do understand most of the problems are in the plumbing lines.

In order to drain the tank upon completion, the water pump will need to run for a considerable amount of time. Is there any down side to having water pump running for a long time to flush out the lines?

Any and all suggestions are welcomed

We followed Peggy's instructions and successfully cleaned our steel tanks. Make sure you run all the faucets until you smell the bleach, then let it sit the prescribed time. We did need to flush many times using our house pumps to clear the tanks afterwards.

I didn't like the amount of time we ran the pumps either. I have since rigged a 12v bilge pump and long drain hose to empty the tank when needed. Much better for the house pump.

You also need to consider your watermaker, if so equipped as the bleached water cannot be run through the systems membrane (per our manufacturer).

We also added a cheap whole house water filter after the house pump which eliminates any residual smell/taste. This was a <$100 investment and uses the same filters as my watermaker.

Seeing my name being taken in vain doesn't guarantee that I won't be able to resist chiming in, but the odds are pretty good that I won't...

I have seen Peggie Halls post on shocking water tanks. What I am not sure about is the amount bleach to be mixed in. I have a 144 gallon tank, am I correct in calculating a gallon of bleach? (Assuming 16 cups to a gallon).

This is an excerpt from Peggie Halls post on Trawler Forum:

1. Prepare a chlorine solution using one gallon of water and 1/2 cup (4
oz) Clorox or Purex household bleach (5-7% sodium Hypochlorine
solution). With tank empty, pour chlorine solution into tank. Use one
gallon of solution for each 5 gallons of tank capacity.

The simplified ratio is 1 gallon bleach=50 gallons water.

Also is doing a treatment with half a tank of water and taking the boat out for the day a good way to wash out the tank?

Unless yours is a sailboat and you can tack a lot in a good stiff breeze, you're not likely to create enough sloshing in the tank to clean more than about 10% above the waterline in the tank.

Is there any downside to doing this? I do understand most of the problems are in the plumbing lines.

Most, but not all.

In order to drain the tank upon completion, the water pump will need to run for a considerable amount of time. Is there any down side to having water pump running for a long time to flush out the lines?

As long as the pump isn't allowed to run dry, it shouldn't be a problem unless you water pump is already on its last legs. Run the pump to drain at least half the water 'cuz draining the tank into the bilge instead of running the pump won't do much to flush the nasty water out of the plumbing...a lot more rinsing will be required, which kinda negates any gain from draining into the bilge. Besides, you don't want all that bleach in the bilge unless you want to turn a simple water tank recommissioning job into a major bilge cleaning too.

I have read, been told, etc, that bleach is bad for aluminum tanks. It was decreed by these wise souls that one should only do the bleach soak on the lines and not the tank if aluminum.

Is this true?

I love you Peggy !!! Glad to see you here. But, if I make a bunch of expletive laden comments, then add "Peggy Hall" and maybe "head mistess" will I get your attention everytime.

cardude01 said:

I have read, been told, etc, that bleach is bad for aluminum tanks. It was decreed by these wise souls that one should only do the bleach soak on the lines and not the tank if aluminum. Is this true?

Click to expand...

Yes...and no. Yes, chlorine is corrosive and will damage metal tanks. However, you're carrying chlorinated water that remains in the tank all the time, the cumulative effect of which will corrode a metal tank over time...which is why the average lifespan of an aluminum water tank is only about 20 years.

The bleach solution used to recommission the system is only in the tank a few hours...not long enough to have any real impact. So as long as it's thoroughly flushed out immediately, at worst an annual recommissioning MIGHT take a couple of months off an aluminum tank's lifespan.

Otoh, adding bleach to each fill in an effort to avoid the effort of recommissioning annually or semi-annually will definitely have a negative impact on any metal tank...and without doing much good. 'Cuz the purifying properties in chlorine evaporate within 24 hours, leaving only chlorine's corrosive properties in the water in your tank. The cumulative effect of doing that can take several years off the lifespan of not only a metal tank, but the plumbing too...which is the reason why the "wise souls" advise against bleach at all.

..If I make a bunch of expletive laden comments, then add "Peggy Hall" and maybe "head mistess" will I get your attention every time.

Not likely...'cuz one of the moderators would be sure to see it and delete it before I'd see it.

Excellent explanation. Thanks.

Thanks for the post! I have a 40 year old boat with a slightly mildew smell in our water. We use it to bathe and wash disses but bring our own water for drinking and coffee. I'm going to give this a shot in the spring.