napa I have 2 Rinnai tankless hotwater generators in series and I had to install a recirc pump since my generators are directly under the master suite (nice) but 88 feet away from the kitchen (long wait). The way I hooked mine up was to actually bypass the tankless hot water generators becuase I did not want the generators to cycle just to maintain hot water in the recirc loop. Instead, i bought a small 4 gallon electric tank and use the small tank to maintain hotwater in the line. If you go this route, then you can use a very small pump (i used the smt-303 laing pump that consumes 30 watts of power - see http://www.hvacquick.com for info). The recirc loop is connected to the main hotwater supply line just after the output of the hotwater generators - and then at the distant end just before all the branch lines going to various sinks. The supply side of the loop starts as 1 inch and then goes to 3/4 inch CPVC. The return loop i installed is 1/2 inch CPVC. I insulated the entire loop. The return side of the loop dumps into the 4 gallon tank and then on to the pump which pushes the hot water into the supply side of the loop. I also have a few shut off valves, a bleeder pipe& valve to remove air (very important), and an air vent (also very important). Laing now makes a new pump that has an integrated check value in it and that made the plumbing easier. I did not see that listed on the hvacquick site - call them and ask about the new pump. otherwise, you have to install a seperate check value - not a big deal, but the value must be matched to work with the pump (the output pressure of the pump is low). I used the white paper on the hvacquick.com web site (i think Laing also has some info on their web site) but modified it a bit for the tankless connection. This all started out when I wanted to supply my humidifiers with warm water and I realized that the tankless hot water generators would be kicking on and off whenever the hvac turned on - not waht I wanted. At the same time I then discovered the hot water delay issue. So my recirc system was designed to serve two puposes. I tapped off the recirc loop to supply 2 humidifers and it also keeps hot water in the line for the sinks. It works quite well. Whenever we turn on a sink at the distant end, we have a short delay (about 15 seconds) for the hot water in the recirc loop to push though the branch lines. The hot water generators kick in to backfill the hot water we use with a new supply of hot water. Whent he humidifiers kick in - the flow rate is so low that the hot water generators don't kick on (what I wanted) and the line is backfilled with a small amount of cold water. The small hot water tank then heats the water in the loop to the preset temp.

Condensate pumps collect waste water and pump to drain, comfort pumps recirculate domestic hot water. Which is it?

I just had a chance to live with a gas tankless for a week (Paloma) in a summer cabin I am house-sitting. It was interesting since I've only been around electric demand heaters. My experience is probably old news to some of you, but it was kind of new to me. The first strange thing is the lag time with gas. Electric comes on really instantly. Gas sort of does. When I turned the hot on in the kitchen of the small house, I could hear the Paloma in the adjacent bathroom come on after about 3 seconds. There's probably no way to shorten this time lag. Not counting the ignition delay, you're limited to what you can do. You either need 1) less water in the line between the tank and the faucet, 2) higher water production at the faucet, 3) less heat loss in the pipe, or 4) less pipe. Best would be all four, although you'll have to do a cost/benefit analysis of the expense of the change verses cutting seconds off the hot water delivery time. The solutions are 1) use 3/8th inch delivery line (having 1/2 as much water in the pipe means 1/2 the delivery time), 2) remove any restrictions on the faucet (an air entraining filter might reduce the flow by 1 gph so removing it will cause splashing but reduce delivery time by several seconds), 3) change from copper to plastic pipes or insulate the copper (assuming you have copper), 4) reduce the amount of pipe between heater and faucet (by snaking PEX pipe instead of using rigid pipe). Most of these "changes" are easily installed in new construction but difficult for a retro-fit that cuts delivery time from 30 seconds to 10 seconds. The house where I just stayed has copper pipes that run under the house to the kitchen sink. Total distance as the crow flies is less than 15 feet. Because the copper pipe drops down under the floor into semi-conditioned space, and it was in the mid-30's, the delivery time for true hot water was over 35 seconds. You could tell it was getting warm at about 30 seconds, but full hot water was at least 40 seconds. I could hardly believe it. Because of the lag time during ignition, every time the hot was turned on/off meant there would be a 3 second slug of cold coming down the pipe. The slug would cool off the pipes a little, so full hot was obtained again only after the cold slug was gone for 5 seconds. A gas heater with copper pipe passing through unconditioned space made for a clunky system, but as was posted above, the best solution might be to learn to live with it. My wife and I managed just fine after figuring out how to set the shower temperature and to not use any other fixture when somebody was in the shower. Another alternative might be installing one of the really little demand "hot coffee" type of 120V heaters in the kitchen, depending on why you might want a little hot water really quick. If you're filling the sink for washing dishes, it really doesn't matter if the first seconds are cold. Mark Fleming

I installed a tankless 6 years ago and will never install a tank again. I did it myself and will do it again if I am ever in a new house. I have a 120k Noritz unit that performs flawlessly. I just don't get it guys. Installing a tankless without recirc is like trying to start your car with a half dead battery. Really! "Your builder is right, it defeats the purpose of tankless" nonsense! I did not have recirc initially. I learned by experience you do not just replace a tank with a tankless. It is a bad result for hot water supply. Slow and inconsistent. Internal recirculation tanks might help but never having used one I have no opinion. But unless you circulate water and insulate your pipes to maintain the heat you are really missing the boat. Recirculating inside the heater means your pipes are cold and it takes longer to get to a tap because unlike a tank there is no pressure in the lines to radiate towards the taps. Why store water inside your heater when you need the heat in the pipes for faster delivery? That is just a limited solution to the issue in my opinion. How much does it cost to keep the lines hot. Depends on heat loss and vol. of water in the lines. Insulate!!! I would say my pipes take very little in cost to keep hot. Maybe $5-7 a month. I used 3/4 inch pipe for recirculation to store more water for start up and to feed 110 degree water into the heater. I do not have a timer to shut off recirculation at night so I could save a few bucks if I did that. Its a simple thing to lay out. You go to the last tap in the system and put a return to the heater from there. You need to have a cold water supply for the recirculation. A one way check valve between the recirc and the street supply prevents hot water from pumping back to the street as hot water pressure rises. A second check valve goes between the last tap and where the street supply feeds the recirc line to prevent cold water pressure from the street from back flowing through the hot water lines. Why any builder would not just put a return line back to the heater is beyond me. Its really not a lot of extra work. Especially with all the cheap Pex being used now. A small grundfos 1/25th hp pump is all that is needed in most cases. I use a Honeywell aquastat to trigger the pump. The pump engages maybe once an hour for maybe a minute to raise the water temp from 105 to 110. Heat loss? Did you insulate the pipes you say are losing heat from? You can lnstall a timer to turn off recirc in the night so you use no energy at all. You can do the same during the day when you are not at home. For some families you could have a daily timer that changes recirc to match your schedule. The hot water works with the recirc off, it just does not work properly as iz well known. Tankless is a superior technology. I did not think the endless supply would matter to me, its noticeably better. A tank cools as soon as you start using water out of the tank and cold water replaces it. The temp drops and drops the longer it flows. A tankless heats water on demand and it is maintained at the same temp. Its really is an advantage. But, as has been stated here by users, un managed hot water supply sucks and who cares if it costs a little bit of money to heat and pressurize your pipes so hot water is instant. Its way less expense than keeping 40 gallons of water hot in a tank. I would never heed the advice by someone on this thread that you don't need recirc. Have your builder install a true full house recirculation system. Don't pay attention to this "you don't need it stuff." If the builder balks or talks down to the idea get someone who knows what they are doing to come install it and over ride their obstinate attitude. Just do not listen to the talk of having a better system is not needed. You are going to great expense to have the best hot water supply you can have. Don't let someone with out your best interests in mind wreck your enjoyment of a great tankless system. Recirc all the way!!! Gee people, why would anyone not do this in new construction when its way easier to do.