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Tankless replacement question
As I discussed yesterday, I have a 65 gallon natural gas heater with a recirculating pump system that may have a leak. I'm considering a couple of replacement options, one of which is another tank.
I'm also considering a tankless. There is a significant tax credit and rebate from the gas company for doing that.
Aside from the general pros and cons of tankless, what do you do with the existing recirculating pump/system with a tankless? I suppose one option is to disconnect it.
If I wanted to keep it, how would you design such a system? Would you have the tankless system on the line ahead of maybe a 5 gallon heater that would utilize the existing recirculating system?
Would such a system work and provide the best of both worlds? Or maybe it would cost so much interms of installation and energy use so as to defeat the purpose of saving money with tankless? Also, perhaps such a setup would void any tax credits or rebates associated with a tankless.
If you need a recirc system now...you would still need it. Tankless does not change that equation. Some tankless work with recir, others don't. You need to get installation instructions from your tankless manufacturer on how to install it with recirc
But how does tankless work with recirculating? Would it continuously heat water thar runs in a loop?Originally Posted by jimbo
It would until the temperature stabilizee, but the same thing happens with a tank type.
Licensed residential and commercial plumber
Could you disable the recirculating system?
Sure you can.
Does that slow the hot water down or make it less less efficient?
Any recirc uses energy....a small amount for the pump, and more for the heat loss in the pipe. The better you can insulate the piping, the less heat loss. This energy loss offsets the waste of water waiting for the sink or shower to get hot.
I do not have a circ system because my water is cheap....alot cheaper than the heat loss Jimbo describes plus the energy required to run the pump and the cost to maintain the pump/system.
It comes down to a want rather than a need for me and I chose not to have it. My system is designed properly anyway without a long wait for hot water but with a circ systyem it would almost be instant.
What would you guys do? Get another tank or get the tankless ( I can get around $600 in tax credits and rebates for installing tankless)
Where is your gas meter in relation to your water heater? if you go tankless your going to need to up grade the gas line most likely. That can cost real money......
65 gal tanks are not cheap so tankless should be considered IMO expecially in Florida where you get more bang for your buck becuase of the warm weather.
Last edited by Hackneyplumbing; 02-17-2013 at 02:24 PM.
It's not far from the tank to the meter. The tank is in the garage and the meter is on the outside of the other side of the garage. I may have a 3/4 inch line in the attic space above the garage.
Your water is probably hard. Do you have a water softener? A tankless needs to be demineralized on a regular basis (sort of like a teakettle), or it won't work right - this costs time and money at least on an annual basis. IF you have a large tub or anything that needs or wants a large quantity of hot water fast, that means a bigger unit or multiples in series. They work best at providing a moderate flow. Some need at least 1/2gpm before they'll turn on, so getting warm might be an issue, especially if you wanted it at a low volume. The upfront costs to install one can be substantial if the gas supply is too small or it is located too far away...you might need to go all the way back to the street with new piping and a larger meter. Florida probably doesn't have super cold incoming water in the winter, but that can be a big issue further north where (at least mine) approaches freezing temperatures in the winter. This means you must supply a lot more heat than you would if your incoming water was say 50-60 degrees.
Some tankless systems will not work out of the box with a recirculation system, and on some, it will void the warranty. Many can be made to work with one, but it often gets more complicated. Since the thing should be demineralized on a regular basis, if it doesn't come with it (most don't, but I haven't looked at all), you need the 'optional' cleaning kit, which adds to the costs. Any tankless will end up more expensive to install, and the $600 credit probably won't come close to covering the increased cost to install verses a tank. A good tank these days is quite well insulated, and standby losses aren't all that bad.
From my calculations, if you have to throw away a couple of gallons of water nearly each time you want hot somewhere, (remember, while you don't get to use those gallons down the drain, you still are heating them plus paying for the supply and sewer costs) a recirculation system that runs on a timer, rather than 24-hours, ends up being either cheaper, or within very close to the cost of throwing away all of those gallons, not counting your time and convenience of having it nearly instantly. This assumes you've insulated your lines. The pump on a recirc system is quite small, and does not take a lot of energy to run.
Jim DeBruycker
Important note - I'm not a pro
Retired Defense Industry Engineer
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