Tankless water heater vent sizes and configurations

Phisherman · 2009-08-06T12:48:05+00:00

I plan to purchase a tankless water heater to replace a failing watertank. The current vent is a 6" diameter vent pipe. I need a 7.4 GPMunit (4 bathroom house with 3 showers) and considering a RheemGT199PVN. I noticed some tankless heaters have two separate ventpipes (one intake and the other exhaust). Some have one vent pipewith one pipe inside the other. If I choose the later I will need anadditional hole in the side of the house (no chimney). What are thepros and cons of two separate pipes than just one pipe with aninterior pipe? Are two separate pipes functionally better than onepipe inside the other? I'm a bit concerned when I need to replace thenew heater (hopefully in 10+ years) that I may have to deal withpatching or resizing holes. I've seen so many different kinds andconfigurations in water heaters and vents. Unemployed right now, Idon't have $1600 to spend on installation, I got the time to do itmyself. Any tips on installation are appreciated.

Aug 06, 2009 21 Replies

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bob haller 16 years ago

aving to go

dont hate them just dont believe they are practical except in very special circumstances.........

I post the downsides which unfortunately is a long list...

the vertex is very close efficency wise, without the downsides

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Phisherman 16 years ago

I talked with a licensed plumber and he does not recommend tankless due to the expense and complexity. I called GE and they are giving me a replacement under warranty. The replacement tank will need an expansion tank, the reason (according to GE) the first one failed. I know (liquid) water does not expand much when heated, but apparantly enough to cause a water tank to fail.

Tankless are generally not recommended by plumbers, but they are improving.

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