Do I need to re-do this water heater vent pipe?

Reply

  #1  
Old 08-15-18, 05:00 PM
F
Member
Thread Starter
Join Date: Aug 2005
Location: USA
Posts: 346
Received 0 Votes on 0 Posts
Do I need to re-do this water heater vent pipe?

I think I accidentally chose the wrong forum, but don't know how to move the post! Installed new water heater, but I'm getting pretty bad back-draft. Vent pipe feeds into chimney (nothing else using the chimney for exhaust). The original pipe coming out of the chimney is pretty horizontal. Should I cut it back as far as possible to get more of an angle at the top? I know that the straight pipe is not quite straight, either, but I don't think that's causing the problem. Backdraft odor is pretty strong today, so I want to address this ASAP. Thanks for your help!
 
Attached Images   

Last edited by flukeslapper; 08-15-18 at 05:03 PM. Reason: Wrong forum selected
Sponsored Links
  #2  
Old 08-15-18, 07:20 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 59,709
Received 1,176 Votes on 1,090 Posts
Thread moved to water heater forum.

Hmmmmmm..... I don't think that short piece of horizontal pipe at the top is the problem.
When do you smell exhaust gases...... when the water heater is on ?
Does that water heater have a standing pilot light ?
Is that water heater in an airtight closet ?
 
  #3  
Old 08-15-18, 08:06 PM
F
Member
Thread Starter
Join Date: Aug 2005
Location: USA
Posts: 346
Received 0 Votes on 0 Posts
I'm guessing it has a standing pilot light, but I assumed they all did. It uses a piezo-electric switch to light the heater. I smelled the gas most of the day today, and could actually feel the breeze coming out from between the heater and pipe. Didn't need to do a match test or anything! The backdraft was present while the unit was not actively heating the water. Just checked it now, and didn't feel any backdraft. Should mention that I also felt a strong breeze at the cleanout port, and that has also lessened tonight. There is a rain cap on the chimney, btw.

The heater is in a very tight utility closet, with a louvered bi-fold door for ventilation.
 
  #4  
Old 08-15-18, 08:39 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 59,709
Received 1,176 Votes on 1,090 Posts
I'm not an expert on venting but there should be a natural venting with the pilot light. That heat going up the flue should create a flow of air up. Apparently that is not happening.

Did you have a gas water heater there before ? Was it ok ?
Was something added like an attic vent fan..... something that's drawing air out of the house ?
 
  #5  
Old 08-15-18, 08:59 PM
F
Member
Thread Starter
Join Date: Aug 2005
Location: USA
Posts: 346
Received 0 Votes on 0 Posts
UPDATE: I just did some research, and it looks like the water heater being "orphaned" by the high efficiency furnace could be at least part of the problem. Chimney might be too large for the small amount of heat generated by the water heater alone. Too bad they don't warn you about that when they install the furnaces, huh?

Well, I think it's TRYING to naturally vent upward, but sometimes the air flow just seems to reverse itself. Today, it wasn't particularly windy, but the downdraft was strong. The water heater is exactly where the old one was. There is an attic fan, but I installed that years ago. Originally, the furnace also vented into the chimney, but that ended when the high-efficiency furnace was installed. That was also done before the water heater replacement, though. It's a little freaky, huh? Good thing I recently replaced my CO2 alarm. ;-) I might have a go at modifying that pipe run tomorrow, just for kicks.
 

Last edited by flukeslapper; 08-15-18 at 09:44 PM. Reason: Update
  #6  
Old 08-21-18, 11:22 AM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: United States
Posts: 10,700
Received 92 Votes on 82 Posts
I once had an older house I was selling that had a similar problem that was discovered by the gas company when doing their inspection for the buyer. The gas man had me to remove the draft hood from the top of the water heater and connect the vent pipe directly to the top of the water heater (without draft hood). I had never seen this done before so in my mind I questioned it, but I did exactly what he told me to do anyway to not hold up the sale. I never heard of a problem after that. Thinking back, that had to be 30 years ago.
 
  #7  
Old 08-21-18, 11:33 AM
F
Member
Thread Starter
Join Date: Aug 2005
Location: USA
Posts: 346
Received 0 Votes on 0 Posts
Interesting idea, CasualJoe. I looked it up, and the cons seem to outweigh the pros. My first concern was that it could possibly extinguish the pilot (apparently, it can). Also, it can cause a dangerous buildup of gases, if the backdraft is strong enough, so it doesn't sound like a good idea.
 

Last edited by flukeslapper; 08-21-18 at 11:50 AM. Reason: updating after investigating suggestion
  #8  
Old 08-23-18, 07:11 PM
steve_gro's Avatar
Member
Join Date: Jan 2004
Location: San Francisco
Posts: 1,092
Received 1 Vote on 1 Post
Is that by any chance venting into a masonry chimney, or it it flue pipe up past the roof line?

If it is a masonry chimney, you could probably line it (put double-wall flue pipe into it). Some places allow flex to serve this function.

If it's flue pipe all the way up, check for any blockage. The vent cap at the top should get an eyeball. And I have seen the inner pipe in double-wall slide free of the section it was in and block the vent altogether.

First step, make sure there are no blockages anywhere.

And I disagree with the gas man -- find the problems and fix it, leaving the draft diverter in place.
 
  #9  
Old 08-24-18, 07:42 AM
F
Member
Thread Starter
Join Date: Aug 2005
Location: USA
Posts: 346
Received 0 Votes on 0 Posts
Thanks for the response, steve_gro. Yep, masonry chimney, so it's a case of orphaned water heater exhaust. Of course, when they replaced the furnace, they never mentioned that potential issue. Looking into liners to resolve it. I checked for blockages, and it's clear. I'm with you on the draft diverter - it's staying put. Have a good weekend!
 
  #10  
Old 08-24-18, 08:23 AM
B
Member
Join Date: Oct 2008
Location: New England
Posts: 10,523
Received 37 Votes on 34 Posts
Hi fluke, a couple of points I didn't see or missed. I'm not a pro on water heaters but used to deal with backdraft issues as part of my energy auditing, now retired.
1. A naturally drafted water heater is the most sensitive combustion appliance and most likely to backdraft.
2. Some backdrafting is expected at the start of a heat cycle but should establish a proper draft quickly, I can look up the max time but around a minute.
3. Testing for backdrafting is more than just seeing how it is doing at the moment. Several appliances, dryer, bath and kitchen fans, central vac, air exchangers, attic fans (as mentioned) and window fans are some (most) on the list. When we measured the pressures next to a water heater we opened and closed doors and turned on related appliances to create a worst case condition, thus ensuring that at no time would backdrafting occur.
4. In most cases the exhaust from a water heater should be low risk, until the combustion process malfunctions and it becomes deadly, the CO you mentioned.
5. CO detectors are slow and not as sensitive as you would hope for, not the fail safe they imply.
6. Being orphaned is as you suspect probably the major contributor, but there are many articles about this issue and once a new liner is installed you should review worst case conditions to be sure all is safe.

Best,
Bud
 
  #11  
Old 08-24-18, 09:11 AM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: United States
Posts: 10,700
Received 92 Votes on 82 Posts
And I disagree with the gas man -- find the problems and fix it, leaving the draft diverter in place.
I disagreed with the gas man too, but I wanted that house sold.
 
  #12  
Old 08-24-18, 01:35 PM
F
Member
Thread Starter
Join Date: Aug 2005
Location: USA
Posts: 346
Received 0 Votes on 0 Posts
Thanks for the great response, Bud! I've been keeping a close eye on the bugger, and it normally seems to vent okay so far. I guess certain combinations of outside and inside pressure conditions make it misbehave. At least now I have a better understanding of the situation, and the steps to take.
 
Reply
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: