OK to downsize water heater?

malex

Time to replace 10+ year old Rheem gas water heater. It's a 50 gal 40K BTU unit and it's never given any problem for our 3 person hh. Recently, after all 3 took showers back to back it did run out of hot water and out came rusty water - hence the kick in the butt to replace the aging heater...

I've been looking at the Rheem Platinum 40 gal 38K BTU unit - I assume efficiency has gone up in the past 10 years and I am not one to want to heat an extra 10 gal on standby but wonder if it will match the old heaters delivery. The spec sheet says it will work for 2-4 person hh and 50 gal is for 5 people+...

Thoughts? Also, are there any better alternatives to the Rheem Platinum 40 gal/38K BTU unit in the same price range?

Thank!

george_42

use either a 40 or 50 gal and set output temp to about 150 or so to kill legionnaires bacteria and put a mixing vale to deliver 120 deg water and you will have all the hot safe water you need

EBEBRATT-Ed

@malex

40 gallon should be fine for three people. Back to back showers or showers and washing machine could be an issue but if usage is reasonable you will have no issues. They have the same size burners so not much difference

Larry Weingarten

Hi, You might test flow from the shower head and if it’s over 2.5 gpm consider getting a 1.5 gpm head that has the Water Sense certification. If you switch to a lower flow head, you can go to the smaller heater with very little concern about running out.

Yours. Larry

Steamhead

With the lower burner input, you may run out of hot water more often.

You are correct that water heaters are more efficient now. If that were my house, I'd stick with a 50-gallon unit.

ChrisJ

Larry Weingarten said:

Hi, You might test flow from the shower head and if it’s over 2.5 gpm consider getting a 1.5 gpm head that has the Water Sense certification. If you switch to a lower flow head, you can go to the smaller heater with very little concern about running out.

Yours. Larry

hot_rod

ChrisJ said:

Larry Weingarten said:

Hi, You might test flow from the shower head and if it’s over 2.5 gpm consider getting a 1.5 gpm head that has the Water Sense certification. If you switch to a lower flow head, you can go to the smaller heater with very little concern about running out.

Yours. Larry

Cast iron radiator behind Jerry

ChrisJ

hot_rod said:

ChrisJ said:

Larry Weingarten said:

Hi, You might test flow from the shower head and if it’s over 2.5 gpm consider getting a 1.5 gpm head that has the Water Sense certification. If you switch to a lower flow head, you can go to the smaller heater with very little concern about running out.

Yours. Larry

Cast iron radiator behind Jerry

Clow gas steam my friend.
That's got a built in boiler.

malex

Thanks all - i'll consider sticking with 50 gal or suffer Kramer hair with the lo flow head... only on the wall will a Seinfeld meme turn into a conversation about Jerry's cast iron radiator...

mattmia2

There is a thread about them on here somewhere from about 10 years ago.

mikeg2015

Basic atmospheric Tank water heaters have a little more insulation now but the basic burners haven’t changed in 20 years. About 75-80% efficient. But why are cheap. So no payback for fancy ones.

ChrisJ

> @mikeg2015 said:
> Basic atmospheric Tank water heaters have a little more insulation now but the basic burners haven’t changed in 20 years. About 75-80% efficient. But why are cheap. So no payback for fancy ones.

I'd be more concerned about the heat going up the chimney than the tank insulation or burner design. There's a ton of heat going up that pipe when the burner is off.

My power vented 50 gallon stayed impressively hot without power for 3 days

mattmia2

My power vented 50 gallon had a ton of standby loss compared to my Superstore.

Conventional gas and electric water heaters used to be cheap, but between the price of metals and oil skyrocketing and requirements to suppress ignition of vapors they are about triple the cost of what they were 20 years ago and making alternatives competitive.

mikeg2015

We replace a lot of parts on power vents. The increase in installed cost probably results in about a 8-10 year payback or longer. Not really worth it in my opinion. A good option for new construction or if you are avoiding reclining a chimney however.

hot_rod

Hopefully those power venters are not PVC vented. The high temperature that migrates up after a burner off cycle can really cook the PVC. Perhaps the worse application of PVC for venting flue gas.

ChrisJ

> @hot_rod said:
> Hopefully those power venters are not PVC vented. The high temperature that migrates up after a burner off cycle can really cook the PVC. Perhaps the worse application of PVC for venting flue gas.

Both mine and my parents are done in PVC exactly as Bradford White said to in the manual and there's no signs of overheating.

I'm also almost positive the blower continues after the burner shuts down for some set period.

hot_rod

ChrisJ said:

> @hot_rod said:

> Hopefully those power venters are not PVC vented. The high temperature that migrates up after a burner off cycle can really cook the PVC. Perhaps the worse application of PVC for venting flue gas.



Both mine and my parents are done in PVC exactly as Bradford White said to in the manual and there's no signs of overheating.



I'm also almost positive the blower continues after the burner shuts down for some set period.

Sure a post purge helps, may as well send more of your heating dollars up the flue.
It's the glue joint that can fail, hard to see and predict that. The flue gas temperature in that center flue water heater is well, well beyond the 140F PVC temperature rating. Mod cons don't generally produce much over the operating temperature of the boiler. If and when they do, time to clean the HX

ChrisJ

> @hot_rod said:
> (Quote)
> Sure a post purge helps, may as well send more of your heating dollars up the flue.
> It's the glue joint that can fail, hard to see and predict that. The flue gas temperature in that center flue water heater is well, well beyond the 140F PVC temperature rating. Mod cons don't generally produce much over the operating temperature of the boiler. If and when they do, time to clean the HX


The blower mixes cool air in to cool the exhaust.

The joints are solvent welded. Why would they fail before the pipe?

Regardless in my case and my parents I'm not concerned. We both keep an eye on things and would likely catch it early.

When I replace my heater if they call for a different material I'll use it otherwise it's staying.

mattmia2

The power vent part outlasted the tank at about 18 years although it was starting to sometimes go out for reasons i didn't want to figure out. Everything looked ok with the burner and the connections and solder joints on the control. i decided it was time to work on the boiler project more quickly when that started happening.

The PVC did not look so great.