Converting from tankless to tank

[LeBlanc]

We purchased the 2300sf ranch house (built in 1991) and it has a Noritz on-demand gas water heater. Bathrooms are directly above the Noritz in the basement.

Originally, I was excited at this new efficiency. I’ve come to realize “on demand” is different than “instant.” We’ve now lived here for 3 months, and I’m ready to place a gas 50-gallon tank heater. My wife is REALLY ready, and it will happen within a month or so, before the basement finishing resumes.

With just the two of us retirees here, a lot of water is wasted trying to get the hot stuff. Descaling has not improved it. My wife’s daily routine is now to heat a pot of water on the stove to wash her face instead of waiting 3 minutes and 20 gallons of water to get it out of the faucet. Cold water sandwiches are not helping anything, either.

I’m not a plumber, but can manage my way around many things. I realize transitioning to a tank involves rerouting of lines, but the thing that has me most perplexed is the PVC air intake and exhaust pipes that each exit at the top of the basement ceiling to the outside of the house.

With a typical tank system, will I need to block the intake pipe and use the other as the exhaust? Can I run metal exhaust pipe and connect to the point where PVC exits the house, or, because the pipes are 4 inch PVC, is a power vent mandatory?

Many thanks for your comments.

 

[Reach4]

Originally, I was excited at this new efficiency. I’ve come to realize “on demand” is different than “instant.” We’ve now lived here for 3 months, and I’m ready to place a gas 50-gallon tank heater.

That won't be instant either, unless you add hot water recirculation.

 

[Sponsor]

 

[LeBlanc]

That won't be instant either, unless you add hot water recirculation.

Thank you, and I agree. We went from a Colonial home with a basement heater and second story showers that took 20 seconds to get hot water, to a ranch that is literally 4 feet away from the tankless that takes 3 minutes, and is inconsistent. I'm actually glad that my wife is asking for something better, so that I don't have to admit my early enthusiasm is now significantly diminished!

 

[Reach4]

I think such a delay is not common to all tankless WHs, even those without recirculation. That is only based on reading. I have never had a tankless, but I have not ruled it out for if my tank fails.

I know somebody with a tank and tankless in series. I wonder how a 30 gallon tank following the tankless would serve you.

You could also look up your existing WH to see what it would take to add recirculation to that.

There are various ways to turn on the circulation. A momentary switch is most fuel-efficient, because you would poke the button some time before washing or showering.

Some use a timer.

Some use a motion sensor to turn on recirc whenever somebody enters the bathroom.

 

[Fitter30]

Compleat model#.
One problem that .5 gpm flow is needed to fire heater. Turn faucet to 100% hot or shower full hot first.
.0268 3/4" m copper gallon per ft
.0132 1/2" m copper

 

[Sylvan]

Compleat model#.
One problem that .5 gpm flow is needed to fire heater. Turn faucet to 100% hot or shower full hot first.
.0268 3/4" m copper gallon per ft
.0132 1/2" m copper

For potable water use Type L copper above ground and Type K for underground

I use type L even for hydronic systems and waste lines with brass DWV fittings

Some codes will not allow M tubing to be used in "plumbing."

 

[Jeff H Young]

throw a 50 down there but keep in mind a normal gas waterheater traditional gravity vented requires type b not plastic on the flue and for combustion air refer to code but that plastic vent wont cut it you probebly have a furnace down there verify youve got proper combustion air

 

[Fitter30]

St. Louis areaother than houses built in and before were L. Two houses I've owned were all M. Retired 13 years they were using cpvc for multi story condos and apartments.

 

[Fitter30]

If you want to keep the efficiecy could go with a indirect tank that would use your water heater to heat the tank.

 

[Master Plumber Mark]

Just throw a 50 gallon rheem power vent water heater in place of that junk.... you can use the pvc venting
and all else should be very easy to do

 

[Breplum]

Personally I would recommend Navien's NPE A2 series with built in recirculation pump and add a dedicated, insulated PEX or whatever recirculation loop all the way to the farthest fixture.

 

[Master Plumber Mark]

Personally I would recommend Navien's NPE A2 series with built in recirculation pump and add a dedicated, insulated PEX or whatever recirculation loop all the way to the farthest fixture.

Both the Navien and a Rheem power vent will pretty much take care of his problems....
I just am not a fan of the maintaince that is necessary with the tankless units.....
In the midwest with the hard water the tankless units
have to be de-limed once a year and companies are chargeing $250-300 to do this service which totally
cancels out any savings you think you have with a tankless.....

most power vent units I have installed are forgotten about for well over 10+ years until they
finally start to leak....

whatever floats your boat .... you do you....

 

[Jeff H Young]

Both the Navien and a Rheem power vent will pretty much take care of his problems....
I just am not a fan of the maintaince that is necessary with the tankless units.....
In the midwest with the hard water the tankless units
have to be de-limed once a year and companies are chargeing $250-300 to do this service which totally
cancels out any savings you think you have with a tankless.....

most power vent units I have installed are forgotten about for well over 10+ years until they
finally start to leak....

whatever floats your boat .... you do you....

Can power vented tank heater utilize the air intake of the existing tankless good idea on power ven t forthe 50 ga tank !

 

[Master Plumber Mark]

Can power vented tank heater utilize the air intake of the existing tankless good idea on power ven t forthe 50 ga tank !

Yes... you have both an air intake and an exhaust port off that tankless unit
The power vented Rheem gas unit only needs a 2 inch pvc exhaust vent going out of the building ...
and it can run about 50 feet which looks like it would work fine ...

I have seen pvc run in sch40 pvc and I have seen a ton of them run with foam core pvc pipe too

you really dont need the air intake and should block it off if you install power vent unit

 

[Reach4]

you really dont need the air intake and should block it off if you install power vent unit

Can you use it, so that you don't create a vacuum in the house, and you don't use up humidified air in the winter? I have friends with what looks like that power vent WH, and it looked like it might have a connection place that could serve as intake air.

 

[Master Plumber Mark]

Can you use it, so that you don't create a vacuum in the house, and you don't use up humidified air in the winter? I have friends with what looks like that power vent WH, and it looked like it might have a connection place that could serve as intake air.

I suppose you could pipe it down to the bottom of the heater and it would work as a air intake.... it would work

 

[Reach4]

I suppose you could pipe it down to the bottom of the heater and it would work as a air intake.... it would work

Thanks. I was thinking I had seen what looked like a connection point up top, which now that I think about it, was silly.

 

[Slomoola]

Not for nothing but that hot only pipe wrap needs some love. Terrible fit with every 90 joint wide open. Very thin insulation wall thickness seen in the pictures.

Both hot and cold need proper insulation.

No wonder you have no hot water with essentially raw copper pipe.

IMO, running a recirc takes away from the so called "benefits" of a tankless. More parts to fail, more money down the drain.

 

[Reach4]

IMO, running a recirc takes away from the so called "benefits" of a tankless. More parts to fail, more money down the drain.

If the recirc runs part of the time, that would be much more efficient.

In water-short areas, saving water is much of the benefit, in addition to not having to wait.