With the shower running 2-minutes, you're wasting around 5-gallons of water. If you don't have a well, (and even if you do, you're wasting electricity to pump it up), and the waste running down the drain (you're paying sewer charges or maybe stressing the leach field), it seems like a really big waste to not consider a recirc system. Keep in mind that you are heating that 5-gallons or so, even though it isn't giving you any benefit in your shower and making the WH look like a smaller one, since you've dumped probably around 10% of it down the drain before you get any hot water to shower with. There are lots of recirc systems. Yes, it's better to have a dedicated return line which might be hard to retrofit, but with the right system, it isn't a really big impact to use the cold water as the return line. I don't have any stock or other interest in this, but nearly 7-years ago now, I installed a RedyTemp unit and I get nearly instant hot water at the shower. I have it set to only get warm at the sink, but the shower is closer. If I flush the toilet, by the time I get to the sink, it has purged the warm water from the cold line, and I have full use of both the hot and the cold. Because it gives you the ability to set how warm the water gets before it shuts off, you can make the system more energy efficient since you have at least warm at the sink all the time, with hot shortly after. In my setup, the shower is closer to the WH than the sink, so it gets hot quicker. Since that hot water has to pass by the rest of the fixtures in my place, I get hot sooner everywhere. Tests have shown, a properly setup system, used during 'normal' hours (shutoff overnight) saves energy. Even if it didn't, the convenience is worth it to me. WHen I remodeled, I ran a drop to put a receptacle under the vanity. Once there, it took all of about 10-minutes to hook up the recirc system. Power is usually easier to obtain at the WH, but then you have to do more plumbing to get it all to work. Both types work well.