Tankless water heater?

[Tom the Elder]

My 1951 home has two gas-fired water heaters (lucky me). One is a 40-gallon (!) 20 year old, low NOx tank that serves just the kitchen, laundry room and a half bath. It is located in the laundry room (yep, in the house). My area of CA has hard water (245 ppm) so I am sure the low demand is the reason this tank has lasted so long. Rather than waiting for it to fail, I would like to replace it with a small, gas-fired thankless unit.

With our hard water, I presume frequent (quarterly?) flushing would be needed. Can any tankless unit be plumbed to be easily flushed by the homeowner or are some brands better for that than others? What brand do you recommend for my situation?

 

[Twowaxhack]

You’ll most likely need to upgrade the gas line and the vent.

Rinnai is the brand I like.

The valve kit makes periodic cleaning of the heater a snap.

All that said, it’ll be cheaper to just replace what you have.

 

[havasu]

245 ppm is hard water? Mine comes out of the tap at 515 ppm.

 

[Twowaxhack]

245 ppm is hard water? Mine comes out of the tap at 515 ppm.

That’s terrible

 

[havasu]

Within one year my pool water hits 900 ppm. I feel like Jesus. I damn near can walk across the water!

 

[Twowaxhack]

My tap water PPM on the 700 scale is 60. Ph is around 8

Copper pipe lasts foreverz

 

[Tom the Elder]

You’ll most likely need to upgrade the gas line and the vent.

Does that mean upgrading from the meter, which is about 12 feet from the water heater, or stating at the gas main which is about 60 feet from the meter and runs under 25 feet of concrete slab?

 

[Twowaxhack]

You could run a line directly from the gas meter, that’s my preferred way.

You’ll need 120v electrical connection.

 

[Tom the Elder]

You could run a line directly from the gas meter, that’s my preferred way.

You’ll need 120v electrical connection.

Great! Upgrading gas line from meter shouldn't be too expensive.

 

[fairfieldfanatic]

Just installed a Rinnai natural gas in the garage. It was easier than I expected.
Last year I piped the house for NG. Add up the appliances for total mass flow (BTU). Math said I needed 1.08 inner diameter, so the backbone pipe is 1-1/4 dia. 1” pipe stubs it from there. Yeah, tankless WH consumes over 100,000 BTU, mine is 199,000. So be prepared to address supply. Small residential meters are good on paper for 250,000 BTU. In my area the upgrade to the next meter is 750,000, and these guys do that at no extra charge.
Venting is important. NG combustion yields CO2 and H2O plus any residual stuff, namely sulfur. The sulfur dioxide in NG combusts and leaves sulfur that combines with water and creates a mild aqueous solution of sulfuric acid. Very corrosive, so the venting can not be steel, or aluminum. Gotta be a high temp plastic. Fortunately, if you have a “Super High Efficiency” WH, the exhaust temp will be low, about 120°F.
I can go on and on, but please do your homework. Ask and understand before you begin buying anything.
Good luck.