Recently, I have had questions about the “acidity” of the condensate from 90+% efficient furnaces. These questions have come from architects, engineers, city inspectors and sales people.
As you may or may not be aware, as of May 1,2013 — less than 8 months from now, the new D.O.E. standards go into effect for FURNACE efficiency. This will mostly impact the northern tier of states. Basically, after May 1, 2013, 80% furnaces cannot be installed in the states in blue. (the rest of the D.O.E. requirement for A/C, Heat pumps, and packaged units go into effect January 1, 2015 as of now and subject to change).
Only 90+% efficient furnaces can be installed. Because of this, there will probably be even more questions about the acidity of the condensate from 90+ furnaces. As more people are exposed to the required 90+% efficient furnaces, that question is sure to arise.
The question I have had is: How acidic is the furnace condensate and will it damage the drainage pipes or sewer system?
The answer is: the typical condensing gas furnace will produce condensate the has a pH ranging from 3.5 (the same as orange juice) to 6.5, but is usually in the 5.0 area.
The rating scale for pH is from 0 to 14, with 7.0 pH being the neutral center line, neither acidic nor alkaline. Numbers below 7 indicate an acidic condition and numbers greater than 7 indicate an alkaline condition. [now we are becoming chemists :>)].
Since 90% efficient furnaces have been around since the mid 1980’s, testing has indicated and history has confirmed that there are no long-term effects from discharging condensate from high-efficiency gas furnaces into either municipal or on-site sewer systems. One of the reasons is that most residential waste water discharge is slightly alkaline. By adding slightly acidic furnace condensate, the resulting waste water will tend to approach a neutral condition. Actually, the furnace condensate helps because most public sewage systems will add acid as part of their process to correct the pH to a neutral condition. Because of this, most local regulations that had required neutralizers to be used in the past have now dropped those requirements. You will still need to check with your local authorities for code requirements in your area. We also state this in the installation manuals that come with our units:
Now, for those areas that will require that neutralizers be used on 90+% efficient furnace, we do have available. through our Source 1, a neutralizer kit part # S1-1NK0301 and refills for those kits for maintenance of the neutralizer part # S1-02630228000.
As the new requirements go into effect, keep this in mind in case you have an inspector or architect who asks you about furnace condensate.
(pH information in this post was from an “M” letter written back in 1997 by an engineer named Dennis Aughenbaugh – furnace production manager for York at that time).