A puddle on the garage floor is the kind of thing you step around on the way to the car and then think about for the rest of the afternoon. Water sitting at the base of a tank is worth taking seriously, but it does not automatically mean the heater is finished. In plenty of Everett homes the real source turns out to be a loose fitting, a tired valve, or plain condensation that got mistaken for a leak, and those are very different problems with very different fixes.
Find out where the water is actually coming from
Start dry. Mop the floor, lay a few sheets of paper towel around the base of the tank, and give it two or three hours. Where the paper darkens first will tell you more than any amount of squinting at the unit.
Then work top to bottom, because water travels. Check the cold inlet and hot outlet connections at the top of the heater, then the temperature and pressure relief valve and the discharge tube running down from it, then the drain valve near the floor. A slow drip from an upper fitting will run down the side of the jacket and collect underneath, which is precisely what makes base leaks so easy to misread. If every fitting above is bone dry and water still appears underneath, the tank itself has likely rusted through, and that is a replacement rather than a repair.
What it usually turns out to be
The drain valve is the most common offender, especially the plastic ones fitted to builder-grade tanks. They weep at the stem after a few years, and sediment sitting in the bottom of the tank keeps the seat from closing cleanly once it has been opened.
The relief valve is next. If it is discharging, something is pushing pressure up rather than the valve simply failing. Thermal expansion is the usual reason, and it shows up more often on homes with a check valve or a pressure reducing valve on the incoming line, which is a common enough setup on newer services around Everett.
Condensation catches people out every winter here. A gas heater refilling with water in the low forties can sweat heavily enough down its flue and jacket to look exactly like a failing tank. It is worth ruling out that the unit is simply sweating rather than leaking before you start pricing a replacement, because the two look identical on a concrete floor.
Making it safe before you touch anything
Kill the energy source first: the gas control to the pilot setting on a gas unit, or the dedicated breaker on an electric one. Then close the cold water supply valve at the top. Leave the tank full unless you actually intend to drain it, and if you do drain it, run the hose somewhere that can take fifty gallons of scalding water without damage.
A tank that is actively pouring rather than seeping is a different situation, and shutting the house water off at the main is the right first move. If that water has already soaked into drywall or gone looking for a floor drain that turns out to be blocked, the drainage side of the problem needs handling before anyone worries about the heater. Everett Drain Cleaning works on homes throughout Snohomish County and deals with the blocked floor drains and backed-up lines that turn a contained leak into a much larger mess.
Keeping the next one further away
Flushing a few gallons off the bottom of the tank once a year keeps sediment from piling up against the base, which is what cooks the lower seam on gas units and buries the lower element on electric ones. While the hose is connected, it costs nothing to look at the anode rod, since a spent rod is the quiet reason a lot of tanks give up earlier than they should.
If the heater sits anywhere that flooding would be expensive, a drain pan plumbed to a suitable drain is cheap insurance. And pay attention to how the unit behaves rather than only to whether it is dripping, because a tank that has started to struggle will often tell you first through temperature. When the hot water runs out faster than it used to, sediment or a failing element is frequently behind it, and that is usually the same decline that ends with water on the floor.
Most base leaks caught early are a valve, a fitting, or a misdiagnosis. The ones that turn into a ruined floor are almost always the ones that got watched for a few months instead of traced in an afternoon.