How did water get in my mower carburetor?

I have a push mower with a Tecumseh 3.5 HP Four Cycle engine. It's about 5 or 6 years old. It is a very basic mower without all the bells and whistles, which is just how I like them, (lightweight). It has always been very reliable and started on the first pull. Late last fall it seemed to be getting hard to start, but I used it one more time and put it in the shed for the winter. I poured a little gas stabalizer in the 1/4 tank of gas that remained.
I got it out last week and it would not start. It had good spark but would not even pop. I sprayed a little gas in the air cleaner and it started for a second. I took the hose off the gas tank and cleaned it. Still no start. I finally pulled the bowl off the bottom of the carburetor to find it full of water and things were getting rusty and clogged. One full can of spray carb cleaner and a rag to wipe away the rust in the bowl, and it started right up and runs great again.
My question is how in the heck did the water get in there? Yes, the mower sits outside at times, and has been rained on. However, I ALWAYS replace the gas cap immediately when I add gas. The gas tank is plastic and has a plastic cap that threads about 3/4" over the fill hole, and closes tightly. There is no vent hole or any hole in the cap, or in the tank. No one else uses the mower. So, how in the heck did the water get in there, and the whole bowl was full of water. I tend to wonder how much more was in the gas tank, so I drained it and refilled, and added some "HEET".
My only possible thought is that it could have possibly leaked into the air cleaner, since that air cleaner is a plastic snap on piece of shit that tends to fall off every so often and never fits well. I might be wrong, but I think that any water that would leak in there would go to the engine, not the carb bowl.... (I think)?
Does anyone have an explanation or suggestion?
I guess next fall I will have to add HEET to all the gas powered stuff before storing it,,,,
Frank
God is alive and well in Iraq
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frankhilbert@_______.com wrote:

You already gave the explanation:

I'll provide the suggestion: store it in your garage or shed.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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there has to be a vent hole someplace in the gas tank, probably in the cap
Mark
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frank wrote: "My question is how in the heck did the water get in there? Yes, the mower sits outside at times, and has been rained on. However, I ALWAYS replace the gas cap immediately when I add gas. The gas tank is plastic and has a plastic cap that threads about 3/4" over the fill hole, and closes tightly. There is no vent hole or any hole in the cap, or in the tank. No one else uses the mower. So, how in the heck did the water get in there, and the whole bowl was full of water. I tend to wonder how much more was in the gas tank, so I drained it and refilled, and added some "HEET"." ---------------------------------- WHEN YOU LEAVE AIR IN THE TANK WATER CONDENSES AS THE TEMPS RISE AND FALL. THOSE CAPS VENT THRU THE THREADS. BEST WAY TO STORE MOWER IS TO FILL TANK ALL THE WAY, ADD STABILIZER AND RUN IT TO GET TREATED FUEL IN CARB,THEN TOP OFF. NO AIR IN TANK MEANS NO CONDENSING OF WATER. LUCAS
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frankhilbert@_______.com wrote in news:jk0ob1dp50dt2r660ahjmjra61hfbs0g2n@ 4ax.com:
<snip>

It's vented, or the gas wouldn't flow out of the tank. Some moisture will form from temperature changes, etc., but keeping it full usually cures that problem. Perhaps the gas can you are filling it from collects some moisture, and it gets in that way?
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frankhilbert@_______.com wrote:

Two common sources:
Water in the gas you are buying. Water sucked into the tank from the tank respiration while sitting. All tanks must have a vent of some type. As they sit idle air is drawn in and pushed back out with temperature changes. Tanks should be either empty or full if it is going to idle for a long time. Partial fills are subject to accumlation of water because of this.
Harry K
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