New high efficiency gas furnaces are amazing pieces of home technology. They are saving the environment and, for those of us more monetarily motivated, reducing our energy bills. With these upgraded furnaces a new problem has developed. They produce a lot of condensate water that has to be removed and drained appropriately. It's not as simple as running it down the drain.
See what’s wrong in this picture of the crawlspace I was in?
Yes, there is a dirt floor and no vapor barrier. Look again, there is another problem more specific to high efficiency furnaces. The furnace condensate line, which drains all the water produced by the furnace, empties straight onto the ground.
New high efficiency furnaces put out a lot of water (actually acidic water, but I will get to that in a minute). There used to be a puddle under this condensate drain line but I placed a 5 gallon bucket under it the night before. In 24 hours this furnace produced around 1.5 gallons of condensate water when the outside air temperature averaged 30 degrees. This furnace came on in November and continued to dump around 1.5 gallons of water on the ground every day. We can estimate that 140 days later around 210 gallons of water was added to the crawlspace! And that’s on top of the normal ground moisture!!
One of the by-products of burning gas, be it propane or natural gas, is water. In less efficient furnaces this water goes up your chimney as water vapor (unless it cools and recondenses on its way up, but that’s another post) along with the other by-products of burning gas. In high efficiency furnaces a second heat exchanger actually takes heat out of the water vapor causing the water vapor to condense into liquid water.
If only that liquid water coming out of your condensate line was clean water there would be no problems. However, during the furnace combustion process water vapor is mixed with nitrogen, which accounts for around 78% of atmospheric air. H2O plus nitrogen creates nitric acid with a pH of 4, plus or minus 1 point. To put that into perspective, acid rain is around 5, orange juice is 3, and pop and beer are 4. While you can drink pop and beer furnace condensate is still not safe to drink.
Anyway, back to why the HVAC installer (who is licensed in Ohio) dumped the condensate on the ground in the crawl space (other than perhaps being lazy). You shouldn’t run the condensation simply down the drain because it can corrode metal (it’s also illegal in some localities). It can harm septic tanks. Run it outside with the A/C condensate line? Not a good idea because the line can freeze over in winter and cause your furnace to stop working.
So, dump it on the ground in the crawlspace is the easy answer. Dumping the condensate on the ground (along with other issues) helped lead to a crawlspace nightmare. Adding all the extra water drove up the humidity level and moisture content of the wood framing. High humidity in crawlspaces can lead to mold and bugs. I’m not going to delve into the other problems encountered in this post but you can read about them in my other posts about crawlspaces. Needless to say, adding moisture to crawlspaces is bad.
The ideal way to deal with high efficiency furnace condensate is to first neutralize it. Various manufacturers make inline condensate neutralizers that bring the pH level close to neutral by simply running the nitric acid over a neutralizing agent. You can see in the diagram below from InterNACHI that the neutralizer treats the water on its way out of the furnace and into the drain.
Neutralizers bring the pH level close enough to neutral to safely run the condensate down the drain. All drains should have an air gap and be trapped. Neutralizers are simple and relatively inexpensive for your HVAC serviceman or other qualified individual to install.