Hot water heater overflows and leaks can result in extensive damages in your home. The seemingly small amounts of water in your water heater pan might overflow, eventually forming molds in carpets as well as permanent stains on walls.
We came up with a list of 5 possible reasons to help you figure out why there is water inside your aluminum water heater pan or plastic water heater pan.
- The Temperature and Pressure Relief (TPR) Is Leaking.
A TPR valve is the small valve placed on the side or top of your water heater with a little flip-up arm that automatically opens when the water pressure or temperature inside the tank is extremely high. The valve discharges water to evade a disastrous tank explosion, and it’s a required element in every water heater.
A slow leak will only strip a couple of times in some hours, so to verify that it’s leaking, you 
need to examine the Temperature and Pressure Relief pipe using your palm to check whether it’s wet. Sometimes, maybe the valve was opened so one could perform a test, but the valve was not reset accordingly after the test.
To fix this, you can try and flip the handle open for a few seconds and subsequently release it to check whether the valve will automatically reset.
Kindly note though, that doing this might just worsen the complication if done incorrectly.
- The Temperature and Pressure Relief Valve is Open As A Result of a High Water Temperature or Pressure inside the Tank.
The second possible reason could be a defective thermostat, or crud and mineral buildup at the bottom of your water heater’s tank making you water boil beneath.
You might own a water heater whose TPR valve pipes bypass the water heater pan to an exterior location. In case you own a water heater of this kind, then number 1 and 2 are not the cause of the water getting collected inside your water heater pan.
- A leaking Drain Outlet at the Bottom of the Tank.
This is the spot that you connect your hose pipe whenever you want to drain the tank. The Outlet might have a minor leakage, so you are advised to affirm whether it’s wet using your palm.
- A Leak on the Section Connecting the Pipes to the Water Heater.
Check around the sections the pipes are connected to your water heater tank. In case any of the sections has been leaking for some time, then there will be a rusty color stain running down from it.
- Your Tank Is Leaking As a Result of Deep Corrosion.
This is the worst case scenario since it implies that you need to replace your water heater. Water heater tanks have a tendency of rusting from the inside out, so most of the times, there are no red flags to notify you that something wrong might be happening.
Nonetheless, a rusty wet stain or corrosion around the tank’s base without drip stain signs on the tank’s side is two early signs of a possible tank leakage.
To avoid any of above and protect your floor from water damaging, a water heater pan is highly recommended to use under your water heater.