Need Advice Replacing a 1987 Water Heater

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AlwaysFixingIt

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I could use some advice on replacing my current water heater. It's a 40 gallon atmospheric vent tank water heater with a build date of 1987. o_O

I have to keep a basement window cracked in order to prevent the water heater from back drafting when my dryer is running. This 60 year old house has been insulated, improved windows, sealed, etc.

The unit is near the end of it's life, and I'd like to not worry about make up air when running the dryer. The basement is partially finished, so an open window is not desirable in the winter.

What would be my best option for replacement? Any advice on brands/models?

  • Direct vent heater - Current unit is 16' from exterior wall, so may not be practical.
  • Power vent water - Still would use internal air for combustion, but will this overcome negative pressure with dryer running?
  • Condensing storage heater - Solves makeup air issue, since it brings in combustion air from the outside. The only downside I see is price, the cheapest I've found is $1,600 + installation. I see Bradford White heaters for $2k.
  • Condensing tankless water heater - Solves makeup air issue and I see units for $1,000 + installation. This is tempting.
The natural gas line in the basement is 1" O.D. which is used by a high efficiency, 60k btu furnace and water heater. I live in the northern part of US climate zone 4.

My mechanical room is below a bedroom, so a quiet unit is preferred.
 

Master Plumber Mark

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Why not just install a dryer vent on the basement wall and give your
basement some positive air flow which would probably solve your issues and then
just install a standard cheap fvir gas water heater... that is pretty simple


or you can go the power vented
I am installing a 50 galllon power vented RHEEM gas hot water heater tomorrow They are of a much better quality
than the bradford white units.. all for the low low price of 1899.

I have a 50 galon power vent bradford white that I installed 7 years ago that is now already leaking
and the customer is not happy at all because they are planning on selling the home soon....
 

Dana

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Your gas pipes would have to be upgraded to use any tankless, and at your mid-winter incoming water temps you'll need at least 180,000 BTU/hr of condensing burner to have anything resembling satisfactory hot water delivery. They really only make sense if you need to buy back a few square feet of floor area.

Any power vent would be fine from a backdrafting risk point of view. Cheap power draft units can be pretty loud, but most condensing tanks aren't bad (quieter than your dryer, anyway.)

The HTP Phoenix Light Duty PH76-50 is also around $2K (sometimes less through distribution), but it's all-stainless construction means it should go 20+ years, unlike glass-lined condensing HW heaters. It's only "light duty" in comparison to other commercial HW heaters- it's twice the water heater of a typical 50 gallon power vent. (2x the lifespan, 2x the burner output, 2x the first-hour rating.) Being 16' from the exterior wall is not a problem, the venting an air intake are good for up to 150' (equivalent length of ells added in) according to the manual.

I'm guessing you have what is called an "orphaned water heater" that is contributing to the backdrafting problem, given that your new furnace is high-efficiency, and is probably not using the same flue(?). When a small atmospheric drafted burner is vented into a ridiculously oversized flue, the flue velocity is low, and the liner never heats up to boost the draft. Exhaust also condenses on the liner, and acids in the condensate eventually destroys the mortar in a masonry chimney. With a narrowing chimney liner appropriate for the burner size the backdrafting problem migth be resolved, but it's probably better & safer all around to just go with a power draft or condensing unit.

A 76,000 BTU/hr modulating burner may need a dedicated 3/4" line run back to near the regulator/meter rather than sharing it with a 60,000 BTU/hr furnace, but if it's the first branch off the tee from the meter it'll probably be just fine. (f the pipe diameter is 1" O.D., you're looking at 3/4".)

natural%20gas%20pipe%20chart.jpg


Note, these are "equivalent feet"- the equivalent lengths of the ells & tees have to be added to the lengths of straight pipe.

equivalent-length-flanged-fittings-meter.png
 
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