View Full Version : Hot Water Tank Vent Rise

10-24-2005, 12:07 PM
Hi Guys! First Post! The name is Dave and I need some advice.

Just replaced the Hot Water Heater in my residence, SW PA. New tank is Whirlpool, Natural Gas, LoNox, Flameloc, 40 gal, 62" tall.
I vent out of the vent cap with an immediate 3" 90 degree elbow with 5' of horizontal pipe which then necks up to 4" going thru block wall to vertical stack outside house which rises above roof, total height 15/20'.
Installation instructs calls for .250" rise for every foot of horizontal travel. I just make that requirement but it's there.
Will this setup give me adequate exhaust and no backdraft?

Also, is there a simple test to check for proper draft at vent cap? How do I know the system is working properly.


10-24-2005, 12:23 PM
Light a loosely rolled piece of paper, the blow it out. put it near the vent or flue. It should draft up the stack. If it blows back, your not venting...

10-24-2005, 12:39 PM
Thanks 1.
I tried that last night with wood stick matches. Smoke did not draft into the cap or blow away from in, just floated up. When I moved the match inside the perimeter of the cap it shot up the vent.
It was cold here last night, low 40's.
I'm thinking I got it right but just want to be sure because of the minimum rise on the horizontal pipe.

10-24-2005, 01:55 PM
I think you have it too........

10-24-2005, 04:09 PM
Most manufacturers specify that the flue must rise vertically for a minimum of 6 to 9 inches before the elbow. Placing the elbow where you did can cause too much back pressure. You may have problems with the burner not staying lit.

Did your inspector accept this installation?

Dunbar Plumbing
10-24-2005, 06:27 PM
1/4" per foot or more is legal in your situation. They make a draft gauge that is designed to measure FPM's, Feet Per Minute draw.Most plumbing inspectors in my area require a minimum 300 fpm's draw to be considered safe operation. Most new water heaters and decent flue chases usually pull anywhere from 500 to 700 FPM's.

master plumber mark
10-24-2005, 07:51 PM
the vent rise is only half your problems....

your biggest problem will be in about a year or so from

now when you cant keep your water heater lit.

your biggest problem is you bought a FLAME LOCK
Whirlpool from LOWES and they are nothing but trouble.

here are the cleaning instructions,
eventually you are going to need them


10-25-2005, 08:47 AM
OK, I wish I would have found you guys prior to the purchase, but that was what Lowe's carries and I needed to buy it on a Saturday afternoon!
The basis for the complaint against this item is basically the blocked intake right? As long as I keep the intake clean I should be good. It came with additional filter that wraps around the base for further protection. Heck, I have to change the furnace filter every couple of months!
This was a replacement of an exsisting system.
The height of the heater is 58" compared to a 48" model. Doesn't the additional height of heater assist with the speed of the escaping gases to overcome the quick 90 out of the draft cap. I do have a small vertical pipe installed on top of cap, approx 3"
Sounds like I need a draft flow meter!
That's 300 min for just pilot or with burner on?
And By the Way, I want to Thank you Pro's for getting on these forums to help the weekend warriors. Believe me ! I'd love to call in a pro every time I need something done, unfortuantely economics doesn't allow that, it might if the government wasn't taking so much of the income! Unfortunately we have let the pie get to big and it needs lots of filling!
Thanks Guys!