Is the elevated pH of treated condensate a problem?

BlackCatsGreatPets

Hello,

I'm looking for some advice on the best way to manage the elevated pH of treated condensate, if it's something that needs to be addressed.

The pH of untreated condensate from our tankless hot water heater is 3.5.

The condensate drains into a 10.5 quart  container filled with 3M Aqua Pure N050-P neutralizing agent. 

The pH of the treated condensate is around 11.3, which is higher than I expected and might  due to the contact time between the condensate and neutralizing agent.

Is the pH of the treated condensate something that I should be concerned about? If the answer is yes, how would you go about lowering the pH of the treated condensate?

Is there a buffer that I can add to the neutralizing tank that won't react with the  calcium carbonate while keeping the pH below 8 or 8.5?

Thank you in advance for your help.
Caroline

HomerJSmith

I don't think you have a problem. You are probably discharging the condensate into the sewer sys. Better basic than an acid.

The granules of the 3M Aqua Pure N050-P neutralizing agent are very small and are probably disintegrating into the discharge and boosting the reading. 10.5 quart container is a bit overkill for a tankless if it is totally filled with N050-P.

How are you reading the PH of the condensate? If you are using a stick meter be sure and calibrate it to get an accurate reading.

Jamie Hall

Not really a problem. Best bet for bringing it down a little is to reduce the contact time -- a lot. That tank is a good bit bigger than it needs to be.

BlackCatsGreatPets

I initially checked the pH of the treated condensate with pH paper. When the pH paper turned blue, I rechecked the pH of the treated condensate in a second location and the second location was also blue, so I followed up with a calibrated pH meter, and returned a reading of 11.3.

Is there a way to reduce the contact time without replacing the container?

I decided on a 10.5 quart container because I wanted a system that would only require annual  maintenance from the homeowner.

Would filling the neutralizing tank with water so that the water level is just below the discharge valve be a way to accomplish this? 

HomerJSmith

I use this neutralizing kit by Axiom. I have filled it 1/2 full with 3M Aqua Pure N050-P neutralizing agent and it last several years without adding more agent. I have also use the Axiom beads that come with it, but not at the same time.

If you charge it with the Aqua Pure you have to put a stainless steel scouring pad against the outlet (the discharge side) to keep the Aqua Pure granules from plugging the barrier and being washed out of the tube because the granules are so small. I buy the stainless scouring pad at the Dollar Store or Home Depot.

https://www.supplyhouse.com/Axiom-NC-1-AXIOM-NeutraPal-Condensate-Neutralization-Full-Kit

Jamie Hall

BlackCatsGreatPets said:

. ...

Would filling the neutralizing tank with water so that the water level is just below the discharge valve be a way to accomplish this? 

No -- the contact time is determined by the volume of the tank divided by the flow rate of the condensate.

BlackCatsGreatPets

I would like to thank everyone for their  comments and feedback.

I made some modifications yesterday to reduce the contact time and reduce the amount of neutralizing agent inside the container, and when I checked the pH of the treated condensate this morning, it was around 7. Moving forward, I will need to continue checking the pH weekly to get a better understanding of how long 1/2 cup of 3M N050-P is effective.

I've attached some pictures of the set up and some information about the context surrounding the set up.

Prior to this year, the tankless hot water heater was connected to a condensate drain line that runs across the roof between 2 layers of roofing membrane and down the side of the building. The condensate drain line was not insulated; this wasn't a problem unless the 2021 when the temperature outside dropped low enough to freeze the condensate drain line, shutting down the tankless hot water heater for several days. To insulate the condensate drain line, the rooftop deck and roofing membrane would  need to be removed. Until I'm ready to take on the expense, rerouting the condensate drain line to a condensate neutralizing tank just outside of the water heater closet is an arrangement that I think will work.

Thank you again for your comments and feedback.

Caroline

PC7060

You can also mix the neutralizer with a gravel mixture to reduce the concentration by volume.  The stone can be washed and reused when recharging unit. 

HomerJSmith

You can always drain the the buffered condensate in to a 5 gal bucket in the house in freezing weather and dump it in the toilet.

As I would have it, Today, I just recharged my neighbor's condensate neutralizer that I made out of 3" PVC pipe 15 yrs ago for his furnace and tankless water heater with N050. The last time I did it was 4 yrs ago and it still had media in it. Pretty good, I think. The condensate that comes out of it, if it isn't acidic, I don't worry about it.

BlackCatsGreatPets

PC7060, great suggestion, thank you.

HomerJSmith, I hope that the results are similar for me. I decided to give N050-P a try after trialing marble chips and finding that they didn't work all that well.