Acidic Condendsate from High Efficiency Gas Furnaces

[Wade Lippman]

When my high efficiency gas furnace was installed two years ago, the condensate line was installed to pump it outside under the deck where it does no harm.

You might not be cold enough to worry about freezing, but if you are, you had better insulate it.

[John Stankus]

pH of HCl depends on the concentration, but it is about the strongest acid; nearly pH 1 when concentrated.
Coke is about 2.5 and vinegar about 3.

pH will depend on the concentration for all acids.
You have to be careful when talking about strong vs. weak regarding acids.
A strong acid completely dissociates in solution (gives loses an H⁺ ion (though technically it forms a hydronium ion H₃O⁺ but that is another story))
The common strong acids are things like HCl (hydrochloric acid (also known as muriatic acid)), HNO₃ (nitric acid), H₂SO₄ (sulfuric acid), HBr (Hydrobromic acid), HI, (Hydroiodic acid), HClO₄ (perchloric acid) and HClO₃ (chloric acid)

pH is a way to characterize the concentration of H⁺ ions (again technically H₃O⁺ ions)

pH=-log[H⁺] where [H⁺] is the concentration of the H⁺ ions

By changing the concentration I can hit any pH below 7

Weak acids on the other hand do not completely dissociate. An equilibrium is formed where the H⁺ ions are continually coming off and reattaching to the acid. So the concentration of the H⁺ ions will be less than the total concentration of the acid. Now don't think that because it is a weak acid it is not as reactive. Hydrofluoric acid is a weak acid, and it will etch glass.

Water (normal tap water) is usually a bit acidic due to the dissolved carbon dioxide forming carbonic acid. The pH of rain after falling through the atmosphere and absorbing CO₂ can be around 5.7


John (my day job is teaching chemistry)

[David Helm]

You might not be cold enough to worry about freezing, but if you are, you had better insulate it.

ot a problem here.
N

[Mike Henderson]

John (my day job is teaching chemistry)

Thanks for the information, John. I don't remember much of my college chemistry and it was nice to have an explanation.

Mike

[Jason Roehl]

pH of HCl depends on the concentration, but it is about the strongest acid; nearly pH 1 when concentrated.
Coke is about 2.5 and vinegar about 3.

And the pH of your gastric (stomach) acid can be as low as about 1.5...

[Mark Bolton]

pH of HCl depends on the concentration, but it is about the strongest acid; nearly pH 1 when concentrated.
Coke is about 2.5 and vinegar about 3.

No doubt, Regardless I have been installing HE condensing waterheaters and furnaces in customers homes for nearly 30 years. Its a given with any acid the PH is based on concentration. I can choose to wash a concrete/brick job with straight muriatic or dilute it 50:1. None the less, every boiler, furnace, direct vent water heater, on demand water heater, manufacturer calls out their spec's. You can flout your "coca cola is 2.5" spec all you want. The simple fact is the manufacturer of the appliance calls out the spec for their flue requirements. There is a reason all PVC vented condensing appliances spec no foam core.

We can "jack" around about concentration all we want, or just put the appliance in in a way that we meet the manufacturers spec and cover our butts (but you better still pay your liability).