Hot water heaters are among those appliances in the house that never get noticed until they don’t work; others include the dishwasher, the remote to the TV and the motorized feeding trough. So unless you get into the shower and freeze your tuchus off or there are pools of water forming in the area where you have your hot water heater, you never think a thing about it.
Oh – you’ve never had pools of water forming in the room or closet before? Well, lucky you. Shortly after Christmas this year I noticed the paneling under the steps had begun cracking and splitting, similar to when water soaks into the grain. While I’m not the most observant person, I did realize that this was an anomaly that I hadn’t noticed before. After further inspection, I saw that the prehistoric shag carpet that remained only in the closet where the hot water heater was hidden was saturated. Super! Apparently the hot water heater had been leaking for some time, because not only was the carpet and the paneling on the outside part of the waffling soaked, but the plaster inside was crumbly and the hardwood floors were warped, swollen, and a little moldy.
If your powers of deduction are super sharp, you will have realized by this point in my story that – indeed – there was no pan underneath the hot water heater. So more homeowner magic was done: What started as an inexpensive hot water heater pan oversight was transformed into a complete remodel of a far higher dollar value. Voila.
Typically, the hot water heater pan is there to catch overflow from the pop off valve, but when events like a leak from the rusted out bottom happen, the pan is also a must. Unfortunately, my hot water heater fiasco wasn’t the first that I had seen. I’ve seen several homes, generally older ones, where the hot water heater pan is nonexistent. This was normal for the time period during which these hot water heaters were installed. However, hot water heater pans, which come in a few sizes and are made out of aluminum, really should go under any new installs.
If you have an older home and can somehow muster the strength and have the room to play with, it would be a good idea to slide one under your existing hot water heater. The pan will save future headaches and avoid the magic money transformation that I experienced due to my lack of a water heater pan. You can get a pan like this Oatey 20″ Aluminum Water Heating Pan 
I live in Ohio. Though this is over 5 years old, I just noticed this. I have TWO hot water heaters, one on the ground floor, and one on a 2nd floor, and bought pans for both of them. My second floor unit sits in an out-of-sight closet with a wood door that has slats in it. Since we rarely even peek in, I invested in a moisture detecting alarm that feeds a rope line from the battery operated alarm into the catch pan. Hopefully, we’ll be able to hear the alarm at the slightest bit of moisture beginning to drip, and ward off any party crashing through to the lower floor!
The Building Code prohibits the pop off valve (PTR) from being terminated in the overflow pan.
I think the building code prohibits it from being terminated into the drain piping of the overflow pan. It can terminate into the pan as long as there is visibility indicating a problem and at least a 3″ air gap.
For those of you that have washers especially those that have them on 2nd floors they also have pans available to prevent your washing machine from crashing your 1st floor party. Available at most home supply stores for a very reasonable price and certainly better than finding out your homeowner’s won’t cover the “event”.
Good suggestion Todd. As someone who has witnessed 2nd floor to first floor water devastation, it’s a good suggestion. Many newer homes in So Cal are being built with the Washer / Dryer on the second floor now. Still makes me a little nervous.