expansion tanks and code

[RustyShackleford]

My current water heater has worked just fine for 25 years, with no expansion tank. However, the friend helping me install a new one advises that code requires one. So I guess we'll have to do it - only $40 and a little more work.

I plan to also install a small 10-20 gallon water heater near the kitchen, which is pretty far away from the main water heater. I'm wondering if code waives the expansion tank requirement for units below a certain size.

 

[havasu]

Why the tanked water heater near the kitchen? They have some pretty inexpensive "on-demand" tankless water heaters for point of use applications. Have you considered installing a recirc. system? I purchased one from Costco a few years back for ~$200, and I had instant hot water at all my taps, with a timer which would shut off the system during times it would not be used.

 

[phishfood]

Since the system is all interconnected with no backflow device or check valve between the two heaters,the expansion tank at the main heater will absorb any increase in pressure the expansion created by the smaller water heater.

 

[RustyShackleford]

Since the system is all interconnected with no backflow device or check valve between the two heaters,the expansion tank at the main heater will absorb any increase in pressure the expansion created by the smaller water heater.

We're thinking to wire the smaller unit "in series" with the big one, IOW the small one has its cold-water inlet attached to the hot water line, so it gives hot water quickly but then gets backup from the big one. Do your comments still apply ? Perhaps you were assuming that's what I'm doing anyhow ? Thanks.

 

[RustyShackleford]

Why the tanked water heater near the kitchen? They have some pretty inexpensive "on-demand" tankless water heaters for point of use applications. Have you considered installing a recirc. system? I purchased one from Costco a few years back for ~$200, and I had instant hot water at all my taps, with a timer which would shut off the system during times it would not be used.

I feel like the recirc system is pretty energy inefficient, since you're effectively adding the surface area of all the hot-water piping to the surface area of your water heater jacket, as far as stand-by losses. But then of course I'm adding the standby loss of the add'l small water heater. And as you say, the thing shuts off a lot of the time.

When you say you purchased a recirc system, there would be quite a bit of plumbing work involved too, right ? I've never really looked at one of those systems. I should check it out I guess.

As far as a small tankless, here are some typical units:

http://www.bradfordwhite.com/images/shared/pdfs/specsheets/217-B.pdf

... if you look at the chart on the last page, it looks like a reasonable flow rate (2-3 gpm) for one faucet at a reasonable temperature rise (40-50 degrees) is going to require 15kw or so. No way can I afford that (electrically). Especially since I've already put in a two 240v circuit subpanel, running off a 50 amp breaker in the main box, and the 50 gallon unit is already on it.

 

[phishfood]

We're thinking to wire the smaller unit "in series" with the big one, IOW the small one has its cold-water inlet attached to the hot water line, so it gives hot water quickly but then gets backup from the big one. Do your comments still apply ? Perhaps you were assuming that's what I'm doing anyhow ? Thanks.

As long as there is no check valve in between the smaller water heater and the expansion tank, you should be good to go.