Mold in fresh water tank

[Brassmonkeys]

We just purchased this boat that has been sitting for probably 5 years. The freshwater tank had been winterized but it sat for so long that mold grew. I am currently filling it with "west marine water tank flush" but it looks like theres a decent amount of mold debris. How can I remove this? The inspection port is abiout 3inches wide.

[tkeithlu]

If you don't have an easy way to drain it, get a small utility pump, such as this drill pump,

https://www.amazon.com/Milescraft-13...%2C1917&sr=8-5

and enough garden hose to send the contaminated water overboard. Add water or deflect a nozzle stream in that 3" hole to wash the walls of the tank. Flush it, and when you've got it about as clean as you can, give it a rinse with a water/bleach mixture. Clorox has some concentration advice here:

https://www.clorox.com/learn/topics/.../?gclsrc=3p.ds

Bleach kills everything living. It attacks lipids, and cell walls from viruses on up are largely lipids. Finally, drain everything and fill with municipal water, which will have a tiny amount of chlorine in it.

Best of fortunes with your new boat.

[Brassmonkeys]

Thanks!

[dksail]

If you have the space, it would pay dividends over time to make your inspection port large enough so you can reach in and clean it. We have 3- 5” round holes, but you may want more depending on your arm size.

We also bought a boat that sat with antifreeze in it for maybe three years and that produced a slimy mold that we washed off with warm soapy water and then treated with bleach and rinsed thoroughly.

It also depends on what your tank is made of when considering treatment.

[peghall]

If the tank is full of mold, so is all the plumbing. So after you've succeeded in cleaning out the tank, you should also recommission the entire system.


I first found these directions for doing that in the owners manual for one of my own boats in 1989 and not only have used them ever since, but have included them in both my books:


Although most people think only in terms of the tank, the plumbing is actually the source of most foul water, because the molds, mildew, fungi and bacteria which cause it thrive in damp dark places, not under water. Many people—and even some boat manufacturers—believe that keeping the tanks empty reduce the problem, but an empty water tank only provides another damp dark home for those “critters.”

There are all kinds of products sold that claim to keep onboard water fresh, but all that’s really necessary is an annual or in especially warm climates, semi-annual recommissioning of the entire system—tank and plumbing. The following recommendations conform to section 10.8 in the A-1 192 code covering electrical, plumbing, and heating of recreational vehicles (which includes boats). The solution is approved and recommended by competent health officials. It may be used in a new system a used one that has not been used for a period of time, or one that may have been contaminated.

Before beginning, turn off hot water heater at the breaker; do not turn it on again until the entire recommissioning is complete.

Icemakers should be left running to allow cleaning out of the water feed line; however the first two buckets of ice—the bucket generated during recommissioning and the first bucketful afterward--should be discarded.

1. Prepare a chlorine solution using 1 quart bleach/50 gal water tank capacity

2. Complete filling of tank with fresh water. Open each faucet and drain cock until air has been released and the entire system is filled. Do not turn off the pump; it must remain on to keep the system pressurized and the solution in the lines

3. Allow to stand for *at least three hours, but no longer than 24 hours.*

4 Drain through every faucet on the boat (and if you haven't done this in a while, it's a good idea to remove any diffusion screens from the faucets, because what's likely to come out will clog them). Fill the tank again with fresh water only, drain again through every faucet on the boat.

5. To remove excess chlorine taste or odor which might remain, prepare a solution of one quart white vinegar to five gallons water and allow this solution to agitate in tank for several days by vehicle motion.

6. Drain tank again through every faucet, and flush the lines again by fill the tank 1/4-1/2 full and again flushing with potable water.

An annual or semi-annual recommissioning according to the above directions is all that should be necessary to keep your water tasting and smelling as good as anything that comes out of any faucet on land. If you need to improve on that, install a water filter. Just remember that a filter is not a substitute for cleaning out the system, and that filters require regular inspection and cleaning or replacement.
To keep the water system cleaner longer, use your fresh water...keep water flowing through system. The molds, fungi, and bacteria only start to grow in hoses that aren't being used. Before filling the tank each time, always let the dock water run for at least 15 minutes first...the same critters that like the lines on your boat LOVE the dock supply line and your hose that sit in the warm sun, and you certainly don't want to transfer water that's been sitting in the dock supply line to your boat's system. So let the water run long enough to flush out all the water that's been standing in them so that what goes into your boat is coming straight from the water main.

Finally, while the molds, fungi and bacteria in onboard water systems here in the US may not be pleasant, we're dealing only with aesthetics...water purity isn't an issue here--or in most developed nations...the water supply has already been purified (unless you're using well-water). However, when cruising out of the country, it's a good idea to know what you're putting in your tanks...and if you're in any doubt, boil all water that's to be drunk or used to wash dishes, and/or treat each tankful to purify. It's even more important in these areas to let the water run before putting it in the tank, because any harmful bacteria will REALLY proliferate in water hoses left sitting on the dock.


You're welcome to PM me with questions.



--Peggie

[Caleb_Grey]

Bleach is not recommended, especially if you have stainless tanks, and/or plan on doing this dockside, its not great idea to be dumping bleach into a shared water space.
White vinegar, or hydrogen peroxide are more effective and less harmful to the environment and others property.

[Drek4]

Originally Posted by Caleb_Grey

Bleach is not recommended, especially if you have stainless tanks, and/or plan on doing this dockside, its not great idea to be dumping bleach into a shared water space.
White vinegar, or hydrogen peroxide are more effective and less harmful to the environment and others property.

White vinegar for removing mold, has always yielded poor results for me, bleach is very effective in doing so.
I do agree with you that it's not the best idea to dump bleach in a shared water space.

[JPA Cate]

The reason for not letting it stand more than 24 hrs is that all the chlorine shall have bubbled out in that period of time.

I'm sure Peggy's way will work and take care of the problem. And I would suggest that since it ratio of plain bleach is 1:200 gal. fresh water, it is dilute enough not to be a problem when discharged.

Ann

[peghall]

Note that the directions emphasize that the bleach solution only remain in the systems "at least 3 hours, no longer than 24 hours" before being thoroughly flushed out...not long enough to do any damage to steel or aluminum. Carrying chlorinated water IS damaging...adding a little bleach to each fill does far more.


--Peggie

[GordMay]

Originally Posted by Drek4

White vinegar for removing mold, has always yielded poor results for me, bleach is very effective in doing so.
I do agree with you that it's not the best idea to dump bleach in a shared water space.

Originally Posted by JPA Cate

The reason for not letting it stand more than 24 hrs is that all the chlorine shall have bubbled out in that period of time.
I'm sure Peggy's way will work and take care of the problem. And I would suggest that since it ratio of plain bleach is 1:200 gal. fresh water, it is dilute enough not to be a problem when discharged.
Ann

Originally Posted by peghall

Note that the directions emphasize that the bleach solution only remain in the systems "at least 3 hours, no longer than 24 hours" before being thoroughly flushed out...not long enough to do any damage to steel or aluminum. Carrying chlorinated water IS damaging...adding a little bleach to each fill does far more.
--Peggie

INDEED!

The active ingredient in liquid household bleach is a sodium hypochlorite (NaOCl) solution at 2–10%.

To disinfect, bleach must be applied to a surface that has previously been cleaned. You have to clean, or remove, superficial dirt particles, If you don't clean (physically remove dirt particles) first, then you can't disinfect properly, because the germs are just hiding underneath the dirt.
Bleach is solely a disinfectant, and is inactivated, by microscopic organic debris.
Bleach also rapidly degrades, in the presence of air, light, and heat, and when mixed with water*.

So, after one year (or less), unopened on a shelf, if stored incorrectly in direct sunlight, or at a temperature above 77ºF, it begins to degrade, and continues to deteriorate.
* Pre-mixed solutions of bleach & water remain active for about 1 week.

Because chlorine is not stable in water, it is safe to discharge your (shock) treated water overboard.

When chlorine is added to water, some of the chlorine reacts first with inorganic and organic materials and metals in the water and is not available for disinfection (this is called the chlorine demand of the water). After the chlorine demand is met, the remaining chlorine is called total chlorine. Total chlorine is further divided into: 1) combined chlorine, which is the amount of chlorine that has reacted with inorganic (nitrates, etc.) and organic nitrogen-containing molecules (urea, etc.) to make weak disinfectants that are unavailable for disinfection and, 2) Free chlorine, which is the chlorine that is left over and is available to inactivate disease-causing organisms; it is a measure of the potability of the water. Thus, total chlorine equals the sum of the combined chlorine and free chlorine measurements.

The contact (retention) time, in chlorination, is that period between the introduction of the disinfectant, and when the water is used. A long interaction between chlorine, and the microorganisms, results in an effective disinfection process. The contact time varies with chlorine concentration, the type of pathogens present, pH, and temperature of the water.

“Clorox ® Concentrated Dosage Guidance”
The following guidelines can help you determine how much Clorox® “Concentrated” (8.25%) should be used instead of “Regular” (5.25%) or “Ultra” (6%) Clorox® to achieve the same dosage, in your continuous chlorination disinfection system.
➥ https://www.maine.gov/dhhs/mecdc/env...geGuidance.pdf

“Chlorine Residual Testing Fact Sheet” ~ CDC ‘SWS Project 1'
➥ https://www.cdc.gov/safewater/public...neresidual.pdf

“Chlorine Contact Time for Small Water Systems” ~ Washington State Dept. of Health
➥ https://doh.wa.gov/sites/default/fil...s//331-343.pdf

[GordMay]

Originally Posted by GordMay

... To disinfect, bleach must be applied to a surface that has previously been cleaned. You have to clean, or remove, superficial dirt particles, If you don't clean (physically remove dirt particles) first, then you can't disinfect properly, because the germs are just hiding underneath the dirt.
Bleach is solely a disinfectant, and is inactivated, by microscopic organic debris.
Bleach also rapidly degrades, in the presence of air, light, and heat, and when mixed with water*....

So, I recommend scrubbing, and rinsing, the water storage tank, prior to the bleach shock treatment.