Water Heaters - Tankless water heater venting

1) 5" flex or 5" to 4" adapter does not go over aquastar vent top. Is there something unique about the aquastar interface? Is ther a special adapter for aquastar tankless water heaters?

2) Ceiling passthru. Presently have a 4" passthru. 4" pipe is supported on a saucer about 10' up. Present water heater uses a 3" to go inside. Have not seen a 5" feedthru using the present design at HOme Depot, Osh, ACE? Should I be going to a specialty shop?

3) 5" to 4" at rooftop
Aquastar recomends 5" all the way. Does it make any difference if I go from a 5" to a 4" at my rooftop or do I need to tear up my roof and put a 5" stack in?

I guess you are referring to the Aquastar 125 series water heaters. I know that the 240FX uses 4" vent since I've installed this model. I believe I remember seeing that the 125 requires 5" vent.

If that is the vent diameter required by the installation giude I would not recommend reducing the diameter. The 5" diameter is probably required to properly vent the exhusat gases. I would read the instructions carefully since I definitely remember the 240FX clearly states that the vent has to be single wall stainless steel (not B-vent). B-vent may be OK for the 125 series.

However, as far as I know the 240FX accepted the single wall vent from Home depot without any problem.

1) Yes the 125 does explicitly say 5" and does recommend dual wall. Since I have not dealt with dual wall I am guessing that the dual wall pipe attaches differently? I am assuming the dual wall has a wider diameter and the flange on top of the 125 fits between the dual wall?

2) Still looking for ceiling feedthru for 5" pipe

3) I will do roof installation last to swap out 4" to 5" vent

Thx for your reply

Not having installed the 125 no idea why you are having difficulty with the vent. Why don't you contact CEC's tech support and ask. I have found them very helpful in the past and very good at sending any service info that's not on the web site.

The double wall vent fits the 125 perfectly. I replaced the ceiling feedthru with a 6 inch donut. The 5" line goes straigt to the roof where I replaced the 4" feedthru with a 5" feedthru.

After a few leak checks and putting the shingles back in place I should be in business.

Thx for your help.

Make sure that you maintained 1" minimum clearance to combustible as it goes through the ceiling and/or roof.

thx For reminding me

I am doing some fine tuning on the roof access now to ensure I have the 1" clearance.

After you go through all the trouble to install this uint, I would love to know how well it performs in a few weeks... If it has lives up to your expectations or not.....

please e-mail me sometime with the results..


thank you

makr