Gas water heater venting

**Fidel Gonzales** · 12-31-2011, 07:08 AM

What is the standard height between the vent pipe collar and the top of the unit. The picture depicts my own unit with a 1.1/2 space. I've been seeing unit with 2-3" spacing. The larger spacing may not be venting the C0 properly. Any help/suggestion would be great.

Thank you in advance for any help.

Happy New Year to all. Please stay safe

Fidel

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**Rick Cantrell** · 12-31-2011, 07:17 AM

Since water heaters come with the vent hood, the correct vent hood is the one that comes with the water heater.

**Fidel Gonzales** · 12-31-2011, 07:28 AM

Originally Posted by Rick Cantrell

Since water heaters come with the vent hood, the correct vent hood is the one that comes with the water heater.

Thank you soooo much Rick

**Bob Harper** · 01-01-2012, 07:03 AM

I'd worry about the lack of proper vent rise and if that 3" doesn't increase to 4" to get some lift out of it.

Just understand draft hoods were designed to spill fumes. unfortunately, they work.

**Jerry McCarthy** · 01-01-2012, 08:45 AM

I'd be more worried about the lack of proper rise on the vent connector.

**Gary DeWitt** · 01-01-2012, 08:58 AM

As Jerry and Bob said, you need rise, 1/4" per foot in the connector. The bottom line is, does it vent the appliance without spillage? When I can get to them without a ladder, I'll run the WH for at least 10 minutes and then check for spillage with a mirror.

**Bob Harper** · 01-01-2012, 10:29 AM

mirrors only show if moisture is spilling from that side of the draft hood. If there is no fogging of a mirror, that does not prove the unit is venting properly. You can have a clean mirror with no flue gases making it into the flue. Draft hoods de-couple the vent from the appliance and allow spillage by design. Unfortunately, they work.

**Jerry Peck** · 01-01-2012, 11:37 AM

Originally Posted by Gary DeWitt

As Jerry and Bob said, you need rise, 1/4" per foot in the connector.

And a minimum 1 foot rise before the first elbow.

Looks like single wall vent, where does it go or what does it go into?

**ted kidd** · 01-01-2012, 08:16 PM

Natural draft water heaters should be against the law.

As some have indicated, you may be worrying about the wrong side of this problem. Flue pipe pitch, and chimney lining would worry me.

If you don't have a CO detector or manometer there are some important tests you can not perform. You can at least test spillage at worst case. Turn on all venting devices including dryer, kitchen and bath fans, then fire water heater.

If you burn your hands putting them near the draft hood, the appliance is not overcoming backdraft of chimney. If this persists for more than 60 seconds there is a big problem. A properly drafting water heater, you will feel cool basement air pulling through your hands toward the draft hood, not hot exhaust spilling out.

Often a poorly drafting water heater will have signs of spillage. Scorch marks on tank top, melted pipe insulation, etc.

Cornish Home Inspections · 01-02-2012, 08:09 AM

The drafthood is designed for that particular.

Unless, they switched drafthoods.

You should be checking for proper draft at the drafthood anyway.

No matter the configuration, (unless it's vented thru pvc), turn on the furnace, let it run for about 5 min's. Then turn-up the water heater.
Now, place a lite lighter just at the edge (about 1" away) of the drafthood (not inside). If it's drafting OK, the flame will stay lite, and be draw towards the drafthood. If it's blown-out, that means you have vent gas spillage, or a draft problem. The flame needs air/oxygen, there's none in vent gases.

**Bob Harper** · 01-02-2012, 12:42 PM

Sorry Cornish but a flame drawing inwards only indicates room air being entrained up the vent. There are cases where this can happen with venting failure. The only way to tell for sure if it is venting properly is by combustion analysis and measuring draft pressures above and below the draft hood along with testing along the floor for CO and decreased O2. Its called a Door Curtain Effect. May take more than 5 min. to setup. Cause by high draft.

**Nick Ostrowski** · 01-02-2012, 01:04 PM

The way some houses are built around here, there's almost no way to accomplish 1' of vertical rise on some water heater installs before the 1st elbow.

**ted kidd** · 01-02-2012, 07:34 PM

Originally Posted by Cornish Home Inspections

No matter the configuration, (unless it's vented thru pvc), turn on the furnace, let it run for about 5 min's. Then turn-up the water heater.

Create a powerful draft, then check for draft? Hmmm.

Wouldn't you want to check a COLD chimney rather than a HOT chimney? BPI says start with smallest appliance first...

**Bob Harper** · 01-02-2012, 07:43 PM

Nick. that's true when the chimney breaching or B-vent connection is already 6" below the combustible ceiling above. However, where there is a masonry chimney with the breaching several feet below the ceiling, you can open the basement wall and relocate the breaching where it should be. Better yet, install a listed liner to do it properly. With a 40 K WH, the vent connector should be increased to 4" if less than 3ft of vent rise.