# Duel water heater venting



## MNplumber77 (Dec 23, 2011)

Putting in a whirlpool hottub in new bathroom,slight problem is 40 gallon water heater only pumping out about 26 gal of hot water befor u feel the cold. the tub is 72 gal to over flow... in stead of spending 1k plus on a 75 gal waterheater i thought maybe i could just get a 50 gal to act as a preheat for the main WH, i guess im just woundering if i can feed 2-( 3 inch) vents off a (5 inch) main riser threw roof and still be ok total ftiings would be a tee and 2 90s. Also would this way be even pratical?


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## xyleman (Feb 2, 2011)

what does your gas code say?


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## OldSchool (Jan 30, 2010)

Follow manufacture instruction


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## MNplumber77 (Dec 23, 2011)

hmmph, never been asked that befor. minnesota code book has nothing on gas code so i guess i dont know:blink:


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## xyleman (Feb 2, 2011)

MNplumber77 said:


> hmmph, never been asked that befor. minnesota code book has nothing on gas code so i guess i dont know:blink:


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## RealLivePlumber (Jun 22, 2008)

The answer is in the fuel gas code book


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## Mississippiplum (Sep 30, 2011)

Call a master plumber


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## walker426 (Oct 17, 2011)

MNplumber77 said:


> Putting in a whirlpool hottub in new bathroom,slight problem is 40 gallon water heater only pumping out about 26 gal of hot water befor u feel the cold. the tub is 72 gal to over flow... in stead of spending 1k plus on a 75 gal waterheater i thought maybe i could just get a 50 gal to act as a preheat for the main WH, i guess im just woundering if i can feed 2-( 3 inch) vents off a (5 inch) main riser threw roof and still be ok total ftiings would be a tee and 2 90s. Also would this way be even pratical?


 So you're going to use a 50 gallon to preheat the 40 gallon main tank you better call licensed plumber


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## MSilver (Nov 15, 2011)

We did 2 3" in to 5"... it pass city inspection no problems (In California)


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## bizzybeeplumbin (Jul 19, 2011)

There are places in the UPC for vent sizing, square area. 

It is in our IPC fuel gas code here. 

It doesn't need to be a guessing game or a game of oversize it and it will be fine.


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## Plumb Bob (Mar 9, 2011)

Pay a licensed plumber to install a tankless gas water heater and you wont run out of hot water.


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