Thank you for the link...very interesting info. It's not quite as convenient, but I imagine the On Command or demand system would save a lot on energy costs. The smart system that learns your typical hot water usage and patterns sounds really interesting, though. Any idea what the initial costs are around?

Traditional Water Heaters keep water in the lines hot to cold over distance. A tankless setup won't do that. We find that it takes 2 minutes of full open tap to get hot water in some of our bathrooms. We installed a recirculating pump, the add on kind under a sink. It helps for hand washing, but it's still over a minute to get a hot shower going.

We installed two smaller tankless units, so we could have 3 showers going at anytime and in case one fails, we have another as a backup (which we've had each unit fail twice, so smart thinking on my part). By the way, don't buy Rheem tankless.

Tankless are more expensive, but they do allow for installations on the outside of the house so you could have one at each end very easily.

We have two hot water tanks but there they are joined. One heats the water to 90 degrees and then it flows into the other one which takes up to (not sure what it is set at). When you turn on the hot water it comes from the "hottest" tank. My husband learned about this system of pre heating the water and decided it would work better for us then a tankless system. We never run out but the pressure drops if two sources are both using hot water at the same time.

I would really recommend if you have the space to do it. There will be a little extra cost in the plumbing to the extra tank as in water lines, drain, and gas/propane if not electric.

Our far away bath would take forever to get hot water before we switched to a tankless with a re-circulating loop that doesn't require a tank. It is made by Rinnai and Grundfos, but it is on a timer so not on all the time. The timer sits by the tankless water heater and turns the unit on every so often to pull hot water through the loop. We couldn't find another spot except the attic to put another tank and this was the best solution for us as the unit was placed outside so we even gained space from the old water heater.

Edit: I should note there is no water loss in our system. It just re-heats the water in the return line. No dumping of cold water.

This post was edited by lyfia on Tue, Feb 25, 14 at 11:40

One problem now is that low flow fixtures are the norm. If you have just one waterheater for a house, it may take a very long time to get the hot water to your fixture because so little water flows through the long pipes.

My approach was to use one big gas tankless water heater very close to the master shower and small 80 amp electric water heaters each for the other fixtures that need hot water. I did not plumb hot water lines all over the house but have only cold water lines home run to a manifold. Each water heater is basically next to the fixture (like two feet away from the secondary shower and vanity or four feet away from the kitchen sink).

The gas one provides economic and fast hot water to the main shower while the electric ones were cheap to install and get very little use so the more expensive fuel (electricity) doesn't matter.

we went with a 75 gallon with a recirculating pump. The trouble with tankless can be that if you have a high demand in gallons per minute, your flow rate will suffer, particularly if your starting tap water temperature is cold (we live in a cold weather state).

There are different models of recirc pumps. Ours is a Grundfos basic with an added timer. So it doesn't have to run 24/7. You can also add an aquastat but we didn't do that. The aquastat will just shut it off when it reads that hot water is already in there (like when taking a shower). Just another way to minimize the amount of time the thing runs in a day. I have read here and there about pipes wearing faster with a recirc pump. But here in MI it does take several minutes to get hot water to our showers and faucets. Studies show that you don't really save money with a recirc pump, you do save water but it probably doesn't offset the cost of keeping the water hot in the loop.

But when water is cold 6 months out of the year for handwashing, face washing, etc, it's just not nice. I hope it works out well for us.

good luck on your decision.

We have two in our house now (that is 4000 sq ft) and will also be putting at least two in our new build which will be bigger. I think it depends on how many bathrooms you have and people using them. We have 7 in my family and at least 4 of us shower every day. We are living in a rental now with only 1 water heater and if you don't get your shower first, you are in for a COLD shower! I think you need to do what is best for your family and home situation.

illinigirl, we are also in a cold state. In our current house, it takes close to two minutes to get hot water in the shower away from the water heater. I really look forward to not having that situation in our new house. We will have 3 full baths and it will be likely that some will be used at the same time. I (as I am sure all of you did), am trying to figure out the best way to have enough hot water and hopefully good pressure when multiple locations are being used simultaneously. Obviously want it to be pretty instant, too. I might end up doing the same as you...one large tank with a recirculating pump. Does the pump help with pressure, as well? If not, is there a separate pump that can be installed to maintain good pressure when multiple locations are using water?

I am not DIY, and these are certainly all questions that I will be discussing with the GC and plumber. But I do believe in doing my own research so I can go into conversations with them at least somewhat educated on the subject.

robyn, are your current water heaters right next to each other, or on different sides of your house? I am wondering if it would be more economical to have them together with a recirculating pump or to run more lines across the house and have them on opposite sides.

This post was edited by dreamer16 on Tue, Feb 25, 14 at 12:00

Add to the cost - depends a lot of what type of hot water heater you are using. Electric is cheaper install than NG/propane. Either way, the cost is certainly greater than just the part. But it might only be $200 if electric.

I personally have a recirc pump with a solar tank and a regular tank. All the pipes are insulated so standby losses are not great and we have instant hot water at all taps.

The best solution depends a lot on fuel available. If you have NG or not is a big issue.

Dreamer, we have one on each level so they are not together.

I will have NG available. I was thinking that would be better than electric. I realize the initial costs will be higher...but I am thinking that the monthly costs would be higher with an electric heater.

No, the little recirculating pumps do not help water pressure. Assuming you have sufficient city or well pump pressure, you have the option of bumping up the size of the main pipe runs in your house. Typically, main runs are 3/4" with branches to bathrooms and washers also 3/4". Runs to kitchen sinks, sillcocks, etc. can be 1/2". What can be done is to do the main runs in 1" pipe. It's best for it to be designed into your plumbing system where the gallon flow rate can be figured out to determine the best pipe size, especially if you plan on having fancy showers with multiple body sprays or that horizontal shower I posted about in that other thread. ;-)

If you truly want hot water instantly, no matter the day of the week or hour of the day, you'd be better off with the pump setup that is simply controlled by an aquastat (based on water temperature). If the water cools down, the pump starts and brings hot water to all the fixtures. No timers or smart learning. You will be sure to have hot water instantly all the time. Of course, all hot water lines and the return should be well insulated.

Regarding price, the packages sell for $200 to $500, plus installation plus the extra return line. Not too bad.

Thanks to everyone for the extremely valuable feedback. I am looking forward to going over this with my gc. At this point I am thinking that I like two options the best. One would be a 75 or 80 gallon tank with an on demand pump. It wouldn't be truly instant as you would have to push the button to start it and wait a minute or two. But I wouldn't be wasting all of that cold water and it would consume very little energy in comparison to the recirculation systems that constantly heat the water.

The other option that I like would be two separate tanks on opposite sides of the house. I basically have two baths stacked on one side of the house and the kitchen, laundry and other bath close to each other on the other side of the house. If I had a tank under each area I don't think I'd need any type of recirculation system.

We have a ranch style house and the bedrooms are on one side and the public spaces on the other. Further, I didn't care what it cost or what it took...I wanted an uninterrupted and unlimited supply of hot water for my master bath. So we put in 2 tankless hot water heaters. One on the west side is dedicated to the master bath on one end, the other on the east side does the kitchen, laundry, PR and guest bath, etc. I am delighted. No laundry, toilet flush, dishwasher or anything else interrupts a steady supply of hot water to my shower. Simply a little bit of heaven on earth.

If your plumbing is "split" into two sides of the house, I think two water heaters are an excellent idea.

I have one hot water heater in my house, which is near the bedrooms. I get hot water lickety-split in the bathrooms . . . but it takes forever to reach my kitchen (and probably my washing machine, though I'm much less "aware" of that).

In the house we're building, I was already thinking of two: One near the master bath and kitchen, the other -- probably smaller -- over by the secondary bath.