What is a Bilge Even?! Terms Explained Part 1

pumping bilge water

From the outside, this is what it looks like to “Pump the Bilge”.

Living aboard, there are many phrases and words used that either are unfamiliar to people outside the marine world, OR, are used in a way not commonly understood.


I have to vacuum out my bilge with a wet/dry vac every couple of months. I use a Bucket Head vac.  I love it. I have a traditional (think big) Shop Vac, but I love the Bucket Head. It works, is small, easy to figure out. Yay me! (If you click the link, you’ll see that it has a low rating BUT if you actually read the reviews, you’ll see it’s not because of the vac!)

(And, if I’m being super honest, my older son actually does the vacuuming most of the time these days. Live aboard equivalent to mowing the lawn maybe?)

I have a bilge pump, but, because it’s not set in a “well”, there’s always this layer of water that doesn’t get pumped out. So, on Facebook, periodically on my list of to-dos, I’ll mention “Vacuum Bilge” and folks asked what in the world I meant!

So – the bilge is basically the bottom of the boat between the outer hull and your floor. Depending on your boat, water gets in there from slow (or fast! Yikes!) leaks in the hull, rain leaking through the deck, overflow from the water tank or?? I’m pretty sure my water comes from a slow leak in my water heater and through the bulwark that rotted away prior to my taking on the boat.  The diagram below gives a good visual.

bilge diagram

To determine whether or not it was fresh or salt water, a buddy of mine stuck his finger in there and then tasted it. No joke. It’s fresh. Not salt. That’s a good thing. It means I’m not leaking from the bottom. And, since it doesn’t build up too quickly, I’m not overly worried about it. I maybe should be, but at this point, I can’t do much about it except keep an eye on it and suck the water out.

A bilge pump is exactly what it sounds like – a pump that sucks up water and sends it overboard. It often sits in a “well” – a recessed area that is the lowest point so all the water flows to it. My boat is a flat-bottomed, barge-style hull so the well idea is a little trickier. I’m sure it could be done and it probably should have been, but, alas, I was not the builder, merely the happy buyer. Think of how you tip your glass to get that last bit of chocolate milk sucked up with a straw. That is kind of what a well would do.  Now, imagine running your straw across the flat bottom of your glass. That is basically what my wet/dry vac does.

Do you have a question about a term I’ve used? Ask in the comments and maybe it will become part of a post!

4 thoughts on “What is a Bilge Even?! Terms Explained Part 1

  1. Tamara

    Oh, wow! I understand so much better now! You’re not walking on the bottom of your boat and there’s something else under the floorboards. News to me. This doesn’t have to do with blackwater or graywater though? Where does that go??

    1. outofthebilge Post author

      I’ll admit my ignorance. What is blackwater? Is that sewage? It’s probably in my post about poop. ;)Greywater drains straight from the sink overboard and gets pumped out from the shower overboard. I don’t have any other greywater.

  2. Suz

    Brave soul, to stick his finger in the bilge water and then taste it. I don’t know if I should be impressed or appalled…..

    Nice article. Very informative. Keep up the good work!

    1. outofthebilge Post author

      yeah… i wasn’t impressed! but, it made sense. He was single. No kids. Less to lose I guess!


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