Plumbing for an On-Demand Water Heater?
Posted in Plumbing Talk
I’m considering replacing my 40 gallon water heater with an on-demand gas model. All the home improvement TV shows that have installed one seem to have “home-run” style plumbing (usually PEX) from the heater to all of the taps and appliances, so every tap and appliance is connected directly to the heater with it’s own plumbing.
Is this a requirement for an on-demand system? Could an on-demand heater simply be installed so it can use the existing plumbing?
Georgia
Not only is it not a requirement, it is not even feasible. The cost to re-pipe your entire house to make “home runs” would be 30 or 40 times more than what your new “on demand” (tankless) water heater would cost.
When you replace your water heater with a tankless water heater, you simply hang the unit on the wall where ever the old water heater used to be and connect the two pipes that used to be connected to the old water heater to your new water heater. Lowes sells special flexible 3 foot long copper pipes that are specially designed for hooking up tankless water heaters.
And now a bit more about the “home run” system that you are describing here. They are also called plumbing manifolds. Those systems are mostly installed in some new higher end homes. It is virtually impossible to retrofit them into an existing home in a cost effective manner.
Micah
Yes it can, and I have one myself. one tip. Locate the unit close to an outside wall so you don’t have to spend the extra for the chimney pipe, and just use an “Thu the wall kit”. another tip, supply it with 3/4 copper. this will make the unit come on quicker as it takes about 15 sec. to lite and get HW from the fawcet. You may not like it at first, as its “on demand” but the first month I saved about $20.00 on my gas bill, and never ran out of hot water. Mine is a Takagi Jr. and works great. I have city water, one bathroom and It is undersized for the house, but still keeps up. The key is to use “watersaving fawcets” and showerheads. You’ll be happy with it!
Juliette
I have installed some and so far I have only installed them into the pre-existing plumbing .
The exhaust vent will be replaced with a larger size and the gas supply will too. Probably some supply lines will have to be made up .
If electric you will need a larger electrical supply # 4 should be sufficient.
Personally I’m not a big fan of the home run systems , a bathroom would require 5 lines run , if it is 25 ft or more that can easily add up to a lot of pipe .
So far most everyone likes them but they do take a small learning or getting used to curve. The return for the investment isn’t very quick.
Leia
plumbers always lean to far over and show their buttcrack… ewwyy.. they should get different boxers
Amirah
There is no need to have a home run/manifold system.
Look into the cost/benefit ratio for this type of system. If you have a typical residential home, this unit will probably never pay for itself. It will cost a couple hundred dollars for a new 40 or 50 gallon water heater and a couple thousand dollars for this tankless system (tankless unit, new flue, upsize gasline)
Catalina
they know when you need them simply because of a built in flow switch. i hear they’re real hard to install and not all plumbers are certified to install them. prepare to spend a lot in labor. the reason they used pex is because it was a new system, costs much less than copper and is VERY easy to install. it is commonly referred to as the “lazy plumbers pipe” and plumbers who use it are often ridiculed by their senior plumbers. it is so easy to install a competent homeowner could install an entire system himself during rough in. if you have copper, LEAVE IT! it is just as good if not better than pex, the only difference being is pex is susceptible to damage and can’t be used where copper can. YOU DO NOT NEED A MANIFOLD FOR THIS SYSTEM. it can be installed the same way as normal copper, with specialty t’s and elbows and other such fittings. manifolds are a waste of money, unpractical, spending much more on pex, and there are no long term benefits. i will use pex in my new home when i get one. and have 2 on demand heaters within 10 feet of the sinks/showers so as to not have to wait for the hot water to get there.
~alright, home run manifold does allow for shutting individual problem lines off and eliminates pressure drop from flushed toilets and 2 showers running simultaneously. it also mimics hydraulic lines. minus the return.
~LOL! i have more info on this than actual plumbers! i am an electrician, so i am smarter than plumbers, i can do they’re job just by learning!
Barry
This kind of goes with the old saying, if it aint broke dont fix it. I installed my own Tankless heater, and will give it a 7 out of 10. The biggest issues i have run into is that gas, water in and water out must all be 3/4 inch. This wasnt a very big issue as I had 3/4 on the ceiling but they reduced it down so i just replaced the 10 or so feet to all 3/4 inch. Next is venting. When i got my unit at Menards I was told i could plumb it out the chimney just like our regular tank heater was. WRONG. I was getting backfeed through the furnace, and co2 monitors kept going off. Relized the problem and then vented out the side of the home, no issues since. the system does take a little to get used to such as using small amounts of water for shaving or brush of teeth, if the faucet isnt opened up enough the system wont detect it, and wont heat, thus you get only cold, however if you multitask when another appliance is using hot water or someone else showering, you dont notice this. We have had out dhishwasher, cloths washer, and both my wife and I showering and never ran out of hot water, yes the pressure was reduced but hot water was perfect.
As far as the Pex system, we were informed that if we did any uprading in our house that we would need to change to a PEX design, My wife runs a home based daycare, and the big purpose behind PEX other than reducing cost and not using copper is to get away from the lead based solder pipe fittings
Mina
Bob is right on ! what all the commercials never tell you is the cost of prep & install of a tank-less water heater. The gas requires an evacuation pump and stainless steel flute to remove the heated exhaust. The gas supply line has to be replaced with larger supply line. In most Tank-less water heaters you can’t just open the hot water a little to wash your hands the water is not turned on enough to signal the tank to produce hot water so you turn the hot water at a higher rate. Needless to say like Paul Harvey, the ROI Return on Investment isn’t there when you get
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and their life expectancy is no better than it’s tank counterpart