Medium-size house in New England, 2.5 bath, 4 people. Forced-hot-air heat, 40g gas hot water heater with chimney vent. The original 30gal water heater lasted from when we moved in until 1992, 2nd 40g WH died 2 years ago, replaced with 40g Bradford-white.
We never ran out of hot water until we got the latest WH. However, we always turned the stat all the way up on the WH to extend the hot water. With current tanks apparently you can't turn the stat up that far so we run out of hot water. What to do?
1) looked at tankless – perhaps not ready for prime time. One plumber boasted that "only" 3% of his installs had problems. Also, we have hard town-well water which implies intermittent cleaning. Also, when its 0F out, tankless reduces its flow due to high temp rise required.
2) Looked at "hi-btu" tanks (essentially do what I used to be doing, except the mix-down is at the tank rather than at the faucet) – rare and expensive, which is a shame (also, plumbers said mixdown valve can clog).
3) looked at high-recovery tanks. – they don't help. My problem is running out after 2 or 3 consecutive baths (we have an airjet tub), or 3-4 showers. If it comes back in 30min rather than 60, it doesn't help.
4) looked at std. 75-80gal tanks. Also expensive, and I have a height issue specific to my layout, might have to convert to power-vent (which is pricier and less reliable).
5) looked at adding a 2nd tank in parallel – problem with dissimilar tanks is that one will flow faster than the other (even identical ones get dissimilar with time due to corrosion)
6) looked at adding 2nd tank in series. And…. Can't find any problems! Price is reasonable. First tank will take all the sediment and do most of the heating so 2nd tank should last forever. (so it should be almost as efficient as one tank) I can chimney-vent both (have to replace my 3" sleeve with a 4"). And if one dies I can isolate it and replace at my leisure.
Went through a couple of plumbers before I got to #6 though (Sigh). Any feedback would be welcome, I –think- I'm doing the right thing now…