Q: We have a high-efficiency gas furnace that gets rid of gallons of water. It would be easy to capture this water for reuse, but I've been told this water is acidic, and it might not be good for my plants. Is that true? I'd like to be able to reuse this water if I can, especially on my houseplants.
A: What you heard about this condensate being acidic is usually true. The pH is typically around 5 (fairly acidic), but can run even lower. I've heard as low as 3.5, which is close to vinegar range.
The first thing I'd do is find out exactly how acidic your discharge water is. Garden centers usually sell test strips for water acidity (at least ones with water-garden sections). Some of them will even test water pH for you if you take in a sample. You can also find water pH tests in home centers and online. They're inexpensive. Or you can take a water sample to any water-purification or water-analysis company to see where you stand.
It's possible your system has a condensate neutralizer on it to reduce the acidity level on the way out. If that's the case, your water might be fine already.
If your water is coming out anywhere close to neutral (7 on pH scale), it's fine to use on most any plant. Even down around 6.5 would be fine.
For water more acidic than that, you have two choices. One is to apply it only to plants that prefer acidy soil. Among houseplants, some examples are gardenias, aloe, dieffenbachia, amaryllis, African violets and streptocarpus. Colorado State University has an excellent list of acid-preferring houseplants at
For outdoors, acid-preferrers include blueberries, azaleas, rhododendrons, camellias, hollies, most conifers and hydrangeas that you'd like to bloom blue instead of pink.
The other option is to neutralize the water yourself by either mixing a little lime into the water or by applying lime to the garden soil.
A third option is to consider having a neutralizer added to your drain line if you don't already have one.
Other than considering the acid levels, this water is a good source for recycling onto ornamental plants.