What's the worst that can happen if a water heater is not drained?my wife's water heater is 11 years old and has never been drained.should it be drained after 11 years?and should it be replaced soon or wait till it fails?

I have seen water heaters go 15, 20 years without inspection or any other kinds of maintenance done to them, but the cost of fixing them when they do fail is often higher than just replacing them. A maintenance inspection now I think, would sure tell you where you are at now with this water heater, and then you can decide what course of action is best for you moving forward.

The trick is however is to get a good reputable company that you can trust. Of course if YOU are knowledgeable and handy then a flush would tell you a lot about the health of your water heater. This series of videos should be helpful.

https://www.youtube.com/watch?v=ZIco8uZJq00

While it is good a practice to periodically drain hot water heater, people usually do not do it. Honestly said, most of my customers do not follow that recommendation.

I would not worry too much about your wife's hot water heater for not being drained in 11 years, especially since she doesn't have any problems with hot water system.

If she has frequently clogged aerators, or she notices sediment in hot water, then I would drain it and flush it. Other that that, it is your call

Milo

You only drain a heater when you remove it. If you want to get sediment out you flush it. The difference being flushing has both the inlet and the drain open at the same time, much better than a simple draining. I'd flush yours for about 1 minute. BTW isn't her water heather your heater too?

Usually water heater can live about 15 years but better to check it. But as it was said above fixing can cost much more than just replacing it. If you are handy man you can try to do it yourself but my recommendation is to ask professional help as Plumbers Toronto (http://aqualuxdp.net) for example. They can help you and in case give advice about new heater.