Installing a simple mesh screen on the air vent to your water tank can prevent a lot of problems when bugs want a drink.

Don’t Let Bugs Into Your Water Tank

Every boat has an air vent somewhere for the water tank.  And bugs soon learn that they can get a drink from these.  In the Sea of Cortez, where we spent a lot of time, it was bees that were looking for fresh water.  Cruisers in other areas have told me of problems with mosquitoes, ants and moths.

On most boats that I’ve been on, the air vent is the overflow spigot located by a sink – the spigot you watch when filling the water tank to see when the tank is full.  But it’s also possible that the air vent is on deck somewhere or, on occasion, in the bilge.  On our boat, it was a spigot in the head.

For some reason, these vents are often made without a screen over the opening, which most regular faucet spigots do have.  And thus the bugs can not only get a drop of water right at the opening of the air vent/overflow spigot, but they can crawl inside.

Some will make it into the tank, where they most likely drown, and others may get stuck in the vent and die right there.  That’s how we even discovered this problem.

We were in an anchorage where there were bees.  They had come to the boat looking for fresh water (we knew this as they were all around a bucket that had a few drops of fresh water in it — see photo — and were almost fighting over each individual drop of water in the bottom).  We knew from past experience that they wouldn’t sting us if we didn’t bother them and they’d leave at sunset.

We got the boat closed up and shoo’d out the few bees that had come inside with several mosquito coils, and didn’t really think any more about it other than to plan to move to a different anchorage at first light, before they came back.

As I was cooking dinner, I needed water and turned on the galley faucet.  KA-BOOM!  No air was getting into the tank to offset the water I was taking out – basically an air lock – and the tank walls were sucked in.  The sound was unmistakable as the metal tank flexed.  Dave and I looked at each other in surprise and I quickly turned the water off.  How in the world could we have a air lock in the water tank?

The first clue as to the problem was the back end of a bee sticking out of the overflow spigot.  We assumed that one had gotten in there and gotten stuck, and he had blocked the air.  We removed him with a pair of tweezers and tried running water again.  Nope, we still had the problem.  We pulled more bees out, then had to use a pipe cleaner to clear the bend in the spigot where we couldn’t reach with tweezers.  It seemed that quite a number of bees had gone up the spigot.  Eventually, we got the entire vent clear, evidenced by the tank popping back into its normal position when air finally got through.

Installing a simple mesh screen on the air vent to your water tank can prevent a lot of problems when bugs want a drink.I’m sure there were bees in the tank, but they wouldn’t show up in our drinking and cooking water, thanks to our water filter.  It also removed microscopic traces of them as well as any bacteria that might accompany them.  And the screens on our regular faucet would catch any “bug parts” in the water we used for other purposes – we had to clean them out several times over the next few weeks.  YUCK!

We did not want to have to deal with this again.  So how to prevent the problem in the future?  Obviously, if it had happened once, it could happen again – lots of anchorages had bugs that would come aboard for a drink and we couldn’t totally seal the boat up 100% of the time.

We came up with a very low-tech and cheap solution:  a piece of mesh screen duct-taped over the spigot.  In doing this, you have to be careful that there aren’t any un-taped gaps where the mesh is pleated around the spigot, or bugs will still get in – they’re extremely resourceful!

I’ll admit that this is not the prettiest installation – but it works.  I’m sure that handier people can come up with ways to make it look nicer.  If you do, please add a comment with your idea or send me a photo and I’ll post it here to inspire others.

If you’re not 100% positive that your tank air vent has a screen already incorporated into it, go check it now — before you have a problem.  And if it doesn’t have a screen, tape a piece of mesh screen over it!

Installing a simple mesh screen on the air vent to your water tank can prevent a lot of problems when bugs want a drink.

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  • Chris July on Facebook
    Posted at 03 January 2013 Reply

    Wow, thanks for the great information. I would have never imagined that could happen.

  • Immo Weichert on Facebook
    Posted at 03 January 2013 Reply

    Thanks for the info !

  • Tammy Nielsen Joeright on Facebook
    Posted at 03 January 2013 Reply

    always learning something new here!

  • The Boat Galley on Facebook
    Posted at 04 January 2013 Reply

    Tammy Nielsen Joeright — and really, we learned so much from John on Carolina! Glad to repay even a tiny bit of it!

  • Rick tara
    Posted at 23 August 2013 Reply

    I don’t have that problem but looking at it and wondering about neatness, how about just using a small piece of screening that barely bends around the metal of the spigot opening. Then a neat wrap of tape to seal it up covering maybe less than an inch of the metal?

    • Carolyn Shearlock
      Posted at 23 August 2013 Reply

      Of course that would be better! Somehow, neatness just wasn’t a concern that day 🙂

  • David Hewett
    Posted at 04 February 2016 Reply

    I wonder if a sock would do the trick in “emergency”. Use the sock and some tape until you could make a more permanent fix.

  • S V Bella Nave
    Posted at 14 March 2016 Reply

  • Shari Kurtis Huston
    Posted at 14 March 2016 Reply

    I’ve had ants and once (and only once, thank goodness) the most ginormous spider you could imagine. Ugh!

  • Cathleen Speaker Holzknecht
    Posted at 14 March 2016 Reply

    Dave Holzknecht

  • Michelle Kelly
    Posted at 13 March 2016 Reply

    I am having a problem with the smell of my water! It reeks! What do we do? We’ve used cleaners emptied it, bleach,empty, nothing works. We hav drained it a million times. I can’t use it for anything. We only do weekend trips so we bring water with us, but it is kind of a hassle. Any suggestions?

    • Carolyn Shearlock
      Posted at 14 March 2016 Reply

      Is there any sort of an access port so you can get inside it to check that nothing has gotten in and also to scrub it down? If water is constantly being left in it between uses (and some in the hoses), it could be that it’s just “old water” too.

      • Michelle Kelly
        Posted at 16 March 2016 Reply

        No, no way of getting in it. We have changed all the hoses too. Should we drain it after every trip? How long does it take for water to go bad? There’s an access opening and I can see the tank but there’s no access to the inside of the tank. The hole in the floor isn’t big enough to pull it out either. And we’re not ready to tackle that project yet. Thanks! Will have to see about getting the book mentioned below!

    • Dave Skolnick (S/V Auspicious)
      Posted at 14 March 2016 Reply

      Buy “Getting Rid of Boat Odors” by Peggie Hall. No question that book is the single best resource for keeping your boat fresh smelling.

  • Susan Spiller
    Posted at 14 March 2016 Reply

    Jim Spiller, please read this!!

  • Dawn Read
    Posted at 03 July 2017 Reply

    Reminds me, Lucky Read, will you please find our tank vent and clean our screen?

  • Desiree Verleur
    Posted at 03 July 2017 Reply

    Marlene Smakman

  • Jack Titchener
    Posted at 13 July 2017 Reply

    Great advice for the water tank! We haven’t upgraded our filter lately and have been noticing a few too many critters in our water than we want. I’ll have to remember these tips for when I try and fix the tank. Thanks again!

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