About condensate neutralizer

budalb

I want to ask a question about condensate neutralizer. I have a high efficiency boiler with a condensate neutralizer. The device is a typical horizontal rectangular pump with neutralizing media. When it was newly installed, the pH is ok. But over time, I found that it never neutralize the condensate to pH above 7.

I have studied this for a while. what I found is that this type of horizontal devices has a fundamental flaw. Because most of the space is filled with media increasing the flow resistance, so that the condensate flows over the media (least resistance) with limited contact so that the pH remains low. I rarely saw any negative comments about those devices. Here is my question: Do you test the pH value regularly? and are you getting pH >= 7?

I decided to remedy this and made a vertical 4" pipe (about 12" height) filled with marble chips (from Home Depot). The condensate is fed from near the bottom and exit from near the top. I can easily get pH 7.0. I am wondering why most of the neutralizer is designed to be horizontal with free surface on the top.

Dave Carpentier

I suspect the horizontal units are just for a more universal compatibility. A floor mounted heater would drain fairly close to the floor.
Im leaning towards making my own neutralizer tube in the same fashion you did. I'd like to find a clear lexan tube so I could see how much marble is remaining, but I dont know if lexan (or clear plastic etc) just gets all dirty on the inside with use so that you couldnt see inside anyhow ?

Jamie Hall

pH 7 is entirely reasonable. There is no need to go below that -- nor is there any reason to go much above it. It's useful to remember that you are dealing with a mixture of nitric acid, with a little sulphuric, and some carbonic. It's the nitric which is a nuisance -- but fortunately it is a very strong acid, and thus calcium carbonate (marble) neutralizes it very quickly; contact time is everything.

Alan (California Radiant) Forbes

I'd like to find a clear lexan tube so I could see how much marble is remaining....

I've found that the neutralizing media doesn't substantially get reduced in size over time. It develops a patina or coating and the individual pieces fuse together. The chemistry and the reduction in efficacy is beyond me.

HomerJSmith

Ya, I never test the condensate on a routine basis, although I have. I assume that media is doing its job. Ph 7 is what you get. I use PH tape.

Horizontal condensate neutralizers, like the Axiom, has a direction of flow so that the condensate stays in the media for a longer time. It takes time for neutralization to take place. So, it has to be installed in the proper direction.

I have a paper somewhere on the reduction of neutralizing over time of the media because a film forms on the media which is why it is recommended to change it once a year, regardless.

Smaller media as opposed to larger media is more preferable because of the larger surface area exposed to the condensate. Marble chips are probably not the best media as the calcium is locked in a matrix. There is better media available.

Alan (California Radiant) Forbes

Smaller media as opposed to larger media is more preferable because of the larger surface area exposed to the condensate. Marble chips are probably not the best media as the calcium is locked in a matrix. There is better media available.

I use a combination of both, in layers.

hot_rod

I built a few with 3” PVC and a plugged closet flange. US plastic sell clear 3” PVC in 1 foot increments and it glues like regular PVC

Here was the first version before I found the clear PVC online

I used limestone gravel from my driveway 

budalb

Mine looks similar with yours, but I used a shorter 4" PVC. I found that the diameter is large enough so that the flat end cap at the bottom is stable for support. I decided to not hard connect to the drain pipe and let the neutralizer stand on the ground. It is easier to replace media later.

hot_rod said:

I built a few with 3” PVC and a plugged closet flange. US plastic sell clear 3” PVC in 1 foot increments and it glues like regular PVC

Here was the first version before I found the clear PVC online

I used limestone gravel from my driveway 

budalb

I found that the pH was ok when the horizontal device was initially installed, maybe due to fresh media. Over time the neutralizing over the media is not uniform. The top portion has high flow, so reacting more. For non-marble media, the media reduces in size and shrinks below the water surface, creating a region of less resistance. The lower portion with media can barely flow, losing its neutralizing function.

HomerJSmith said:

Ya, I never test the condensate on a routine basis, although I have. I assume that media is doing its job. Ph 7 is what you get. I use PH tape.

Horizontal condensate neutralizers, like the Axiom, has a direction of flow so that the condensate stays in the media for a longer time. It takes time for neutralization to take place. So, it has to be installed in the proper direction.

Do you still have the paper? I am interested in how long to replace marble chips. I just replace the neutralizer and will see how it functions in the high heating time in the winter.

HomerJSmith said:

I have a paper somewhere on the reduction of neutralizing over time of the media because a film forms on the media which is why it is recommended to change it once a year, regardless.

Dave Carpentier

This is the first Im hearing of changing the media annually. I dont have one yet and I had assumed that the marble or whatnot just gets consumed, so that you just open the top and pour more in.

How about a unit like hotrod's in a 4" form factor, but with a 3" perforated pipe (drainage tile ?) inside it as the media container , that you could lift out and empty/refill ? That would save having to disconnect lines and all that.

mattmia2

I bought 2 of these and have installed one of the 2 so far and like it a lot. somewhere in the instructions it says to rinse off the media periodically if you have aluminum components in the system.

hot_rod

It comes down to how much condensate flows through the media. If your boiler is always in condensing mode, the media will not last as long as on a boiler that runs out of condensing mode. Be tough to predict when a media change will be needed,

I don’t know much harm would come from dumping some slightly low ph down the drain until you replenish?  I suspect plenty of condensers dump into sewers without any treatment 

Back on the farm mine just went out the back of the building into the limestone earth the we lived on🥴
On the house I treated it, concerned about the concrete septic tank.

I know allowing it to flow untreated across a concrete floor will corrode a groove into the slab.

budalb

The best way to decide if you need to change media is to test pH value. The reason to recommend changing media annually is that the marble chips won't be consumed away much. When the marble chips (calcium carbonate) reacts with the acids, insoluble calcium salt precipitates and coats the marble chips, prevent them from contacting the acid anymore. So the neutralizing power deceases without much volume loss.

Dave Carpentier said:

This is the first Im hearing of changing the media annually. I dont have one yet and I had assumed that the marble or whatnot just gets consumed, so that you just open the top and pour more in.

How about a unit like hotrod's in a 4" form factor, but with a 3" perforated pipe (drainage tile ?) inside it as the media container , that you could lift out and empty/refill ? That would save having to disconnect lines and all that.

Dave Carpentier

budalb said:

The best way to decide if you need to change media is to test pH value.

I assume there's no point to testing the ph in late summer as a pre-season check, as the condensate in the tube would have spent a lot of dwell time sitting in the container.
It would have to be testing at a time when a lot of condensate is being generated, a "live test".