Mould in water tank vent pipe

[mikedefieslife]

Seems I've got some mold and grown in the vent pipes for both my water tanks (catamaran).

The fill and the pump pipes are both perfectly clear, so I'm at a loss to understand why it's there. The vent is filtered to prevent bugs etc.. getting in, but all the growth is in the lower part closer to the tank.

Water from the tap looks perfect fine, and I've a seagull filter for drinking water.

Should I just change the hoses and be done with it, or should I unseal the tanks and inspect further?

[Tom Dancs]

Hi,

Every so often, I do a bleach/water (about a cup of bleach for a 15 gallon tank) fill of the tank. I let it sit for a few hours, (maybe sail the boat to let it slosh around), then pump all the bleach water out. Also I remove the vent hose, and use a camelback suck tube cleaning brush with bleach/water solution, to clean it, then put it back on.

After doing that I fill and pump out the tank once or twice, until the mild bleach flavor is mostly gone. Also I occasionally ad a drop of bleach per gallon when filling the tank. Its hardly noticeable, and keeps the tank from growing crap in it.

Regards,

Tom Dancs

[thinwater]

Screening the inlet and using a Seagull is good, but there may be a few more things. I published a bunch in Practical Sailor, and a summary is here:

Sail Delmarva: Drinking Water Filtration--The Short Version

... and far more detail in "Keeping a Cruising Boat for Peanuts."
Sail Delmarva: The Book Store

First, are you filtering the water as you load it? Marina piping and hoses always shed scale and algae. Unless you keep the tank physically clean, like washing dishes, good sanitation is impossible. Keep the crud out. It does NOT need to have carbon, just 1 micron filtration. The Baja Water Filter described in the above book or in PS is a great option (not a Baja fuel filter--totally different).

Second, shock the tank with bleach once a year. Make sure you overflow the tank, to force water up into the vent.

Third, treat the water with bleach at standard dose about once per month. The small amount of chlorine coming off the surface will treat the vents etc. Bleach is good, but Aquamega tabs last MUCh longer (the residual is stabilized).

Finally, the hoses are not hard to clean with a knotted rope and some dish washing soap. Just pull it back and forth.

Not a big deal, and probably not worth replacing them. The new ones will just mold in a month if your practices do not change.

[mikedefieslife]

It's a new (to me) vessel. Seagull filter for drinking water, but nothing else I can see. Doesn't look like there is a filter/strainer on the water fill inlets. Any filter would have to be gravity fed, can't imagine how long that would take to fill two 150 tanks.

Will add come chlorine and do a flush out soon, then just use a small dose as a matter of course. Again emptying the tanks 300l in total is going to take an age. Turn the tap on, wait 15 mins, switch tank, wait another 15 mins.

[Lepke]

Organisms are carried by air, too. With temperature changes and water use, air moves into your tank. If the water is untreated, you get growth starting right away. Warmer climates get more growth.
Marina/fuel dock water often isn't great. Sometimes brackish. I make all my water and it goes thru a sterilizer on the way to the tanks. Even though the water is sterilized, I get growth if the water tanks aren't treated. I use a pool chlorinator test kit and add chlorine so It just show up at the lightest level of the kit. It's below what I can taste. Then I have another set of filters, 1 micron-GAC-CTO, before the galley sink so drinking and cooking water has a great taste. It works better than batch treating and less work, too.

[delmarrey]

Personally, I'd just remove the hoses and clean them with a chlorine solution.

The tanks you can add 5 oz of bleach for each 10 gal of water, which is a safe level for drinking. City levels! As the tanks run out they'll be cleaning themselves. Take the boat out in the rough to get the water to cover all surfaces.
If you add more water before empty, the bleach dilutes down to nothing eventually.

But first, if you have inspection coves, I'd see if there is any sediment in the bottom. If so vacuum it out.
Tanks breathe durning weather changes. When it turns cold at night the air goes out. In the morning warming period the air and pollen/dust comes in.

[Rudderless]

Originally Posted by mikedefieslife

Seems I've got some mold and grown in the vent pipes for both my water tanks (catamaran).

The fill and the pump pipes are both perfectly clear, so I'm at a loss to understand why it's there. The vent is filtered to prevent bugs etc.. getting in, but all the growth is in the lower part closer to the tank.

Water from the tap looks perfect fine, and I've a seagull filter for drinking water.

Should I just change the hoses and be done with it, or should I unseal the tanks and inspect further?

Lots of good advice here about dealing with the mould. The reason you see it in the vent pipes only is most likely because the other pipes aren't open to the environment. The vent pipe will allow for more water vapour movement from evaporation which creates a higher humidity environment. Mould can start growing above 55-60% relative humidity.

In areas that don't get a hard frost, mould will survive year round. Here in Ontario, Canada, outside we typically get between 200-400 mould spores per cubic meter in the winter and between 2000-8000 spores/m^3 in the spring and fall, less in the summer. In Florida you can see outside spore counts of 100,000+/m^3 and some of those spores will be drawn into the tank as you use the water, so even if you have a clean tank and clean water to begin with, you'll get mould if you don't treat the water.

Most people don't have any issues with most mould, but there are some kinds of mould that are very bad for you, like stachybotrys. Luckily, stachy needs around 80%+ RH to propagate, which you aren't likely to see in a vented tank, but can be an issue in areas like the bilge, so it's a good idea to put a little bleach in your bilge water occasionally.

[thinwater]

Originally Posted by mikedefieslife

It's a new (to me) vessel. Seagull filter for drinking water, but nothing else I can see. Doesn't look like there is a filter/strainer on the water fill inlets. Any filter would have to be gravity fed, can't imagine how long that would take to fill two 150 tanks.

Will add come chlorine and do a flush out soon, then just use a small dose as a matter of course. Again emptying the tanks 300l in total is going to take an age. Turn the tap on, wait 15 mins, switch tank, wait another 15 mins.

Please read my "drinking water filtration" link. There are hose-end filters that barely slow the flow (they are under pressure), and the Baja Water Filter will keep up with any hose.

And yes, you should inspect the tank. It should be cleaned and sanitized annually.

As for sanitizing, below is a clip from an article I had published.

-----

The RV code (ANSI A119.2 section 10.8) has a standard procedure that is oft quoted and works very well. I’ve added a few details, but the bones of it come straight from the code and have been reviewed and accepted by the US Public Health Service.

1. Turn off the hot water heater until finished.
2. Remove any carbon canisters or micron rated filters. Remove any faucet aerator screens. Wire mesh pump protection strainers should stay in place. The plumbing will very likely slough off a layer of bacteria during later flushing steps.
3. Clean and remove the vent screen and flush the vent hose.
4. Use the following methods to determine the amount of common household bleach needed to sanitize the tank.
1. A) Multiply “gallons of tank capacity” by 0.13; the result is the ounces of bleach needed to sanitize
the tank. This is 1/8 cup of plain bleach (no fragrance) per 10 gallons.
1. B) Multiply “Liters of tank capacity” by 1.0; the result is the milliliters of bleach needed to sanitize the
tank.
5. Mix the proper amount of bleach within a 1-gallon container of water. This will provide better mixing and reduce spot corrosion of aluminum tanks.
6. Pour the solution (water/bleach) into the tank and fill the tank with potable water.
7. Allow some solution to escape though the vent, if safe and applicable (some boats use the vent as an over flow, while in some cases the vent is in the interior). This will sanitize the vent line.
8. Open ALL faucets (hot and cold) allowing the water to run until all air is purged and the distinct odor of chlorine is detected. Leave the pressure pump on.
9. The standard solution must have four (4) hours of contact time to disinfect completely. Doubling the solution concentration allows for contact time of one (1) hour.
10. When the contact time is completed, drain the tank. Refill with potable water and purge the plumbing of all sanitizing solution. Repeat until bleach is no longer detectable.
11. If the smell of bleach persists after two refill and drain cycles, add a teaspoon of hydrogen peroxide per 20 gallons and mix. The peroxide will oxidize the hypochlorite to chloride (salt) and oxygen, neutralizing the bleach. Any excess peroxide will be harmless to drink and will have no taste. Peroxides are common ingredients in commercially available water freshening preparations. Others suggest vinegar, but vinegar at long dilutions can ferment, undoing all of your hard work.
12. Replace all filters and the vent screen.

Some sailors are afraid of using bleach in aluminum tanks for fear of rapid corrosion. While this should not be a concern if the practice is occasional and the recommended dosage and time is observed, I've tested Puriclean and Aqua Mega tabs to be effective in this procedure and non-corrosive towards aluminum.

With careful selection of dockside water and pre-filtration, this should only be required once per year; even less if the water is very good and the boat is used regularly. Do inspect the tank interior regularly for evidence of sediment, algae, or slime on the walls.

[delmarrey]

One thing to note too, is if your filling your water tanks with city water it maybe already chlorinated already. Using a swimming pool test kit wil tell you the concentration value.

[Dave22q]

I do not see the function of vent pipes over an inch or two terminating in a dust filter. When not using chlorinated city water I will add some bleach at 1 oz to 10 gal more or less.

[thinwater]

Originally Posted by Dave22q

I do not see the function of vent pipes over an inch or two terminating in a dust filter. When not using chlorinated city water I will add some bleach at 1 oz to 10 gal more or less.

1. Because the FDA code says so:
5-302.14 Tank Vent, Protected. If provided, a water tank vent shall terminate in a downward direction and shall be covered with:

• (A) 16 mesh to 25.4 mm (16 mesh to 1 inch) screen or equivalent when the vent is in a protected area; or
• (B) A protective filter when the vent is in an area that is not protected from windblown dirt and debris.

2. Because bugs and mice (no so much on a boat) will climb in and die in your tank. I found bugs in the tank before I added a screen.

Your bleach estimation is for sanitizing only, followed by a flush. For drinking it is far too high, perhaps 10 times, but testing with pool or aquarium strips is best (~ 1ppm residual).

[Rudderless]

Originally Posted by thinwater

2. Because bugs and mice (no so much on a boat) will climb in and die in your tank. I found bugs in the tank before I added a screen.

You've got to watch out for these guys...