Furnace/AC Condensate Drain Options?

[DC73]

Of course I do this to myself two days after the slab has been poured on my new shop. I am now considering a high efficiency natural gas furnace & AC combination. This was in the back of my mind while planning the shop and I thought I would just run the AC condensate drain through the wall. I didn't realize the need for a condensate drain for a furnace. Now that I am considering a high efficiency furnace to go along with that AC, I learn about condensing furnaces and the need for a condensate drain in the winter. I don't like the idea of running a drain through the wall where it could potentially freeze when needed during the winter heating season.

What are my options for getting a functional condensate drain to the furnace location?

The furnace/AC will be installed in a storage room and then inside a (reasonably) air tight sealed closet with fresh air brought in for combustion. The shop will be fully insulated. No walls of the storage room will have plumbing. The shop will have a toilet and a sink in the vicinity of the storage room. Shop is standard 2x4 wood frame construction.

Some options I've thought of:

1) Condensate pump with a line up through the ceiling to the nearest drain. I'd rather find a better option than having to deal with a pump.

2) Dry well immediately outside the building adjacent to the furnace wall. I would have to find a way to protect the drain line from freezing until it gets below grade (very shallow frost line in this area - they bury sprinkler lines only 10 - 12" deep and we don't have to drain them for winter). I might could bore a hole in the slab under the furnace location and then run a drain under the footings (about 16" deep) into the dry well but that may require a lot of effort.

3) I could install the furnace closet in such a way that a drain line could be ran approximately 12' inside an exterior wall to a sink drain. Not sure that gives me enough slope in the condensate drain line. It would also have to make one 90 degree turn. And, the exterior wall will have insulation.

Other options? Recommendations?

Thanks,

DC

 

[Slednut]

I'm far from an expert but I just ran it from the garage under the house then through the foundation. My furnaces flue (PVC)) doesn't produce much condensation and it has never frozen where it exits the foundation.

 

[dfiler2]

I would go with the dry well idea, we're not talking about a lot of water. I have one I did this way a couple of years ago. I ran a 3/4 PVC through a 1 1/2" PVC, then drilled some small holes and filled the void with expanding foam. This pipe went out the wall and down into a 5 gallon pail with holes in the bottom. filled with pea rock, because our frost goes a lot deeper here I also insulated over the top and down the sides of the pail.

 

[DC73]

I would go with the dry well idea, we're not talking about a lot of water.

Hmmm, I wonder if there is a way to estimate the maximum water volume produced? I like the 5 gallon pail idea and your method for insulating the drain. I was thinking it might take a much larger dry well but if the water produced is really not that much and if I could make sure the dry well wouldn't have any capacity issues during peak flow, this might be a good option.

Thanks for the input.

DC

 

[ihrescue]

I have used a condensate pump on my furnace for about 12 years and it has worked great. I ran a temporary clear vinyl 1/2 tubing about twenty feet to the laundry sink. I went to this because the drain that was in place was a hole in the concrete floor that went down to the gravel sub layer. It was always backing up in spite for me sending wire down to insure the hole was clear.

 

[zmaxmotorsports]

Condensate pump and a piece of 3/8" copper tubing will take care of furnace and ac.

 

[FullRaceMerc]

Is heat tape an option? I worked for a restaurant equipment service company. For walk-in freezers the condensate drain was wrapped with a heat tape, then foam insulated. At long as the heat tape was on it worked well. It only had to keep the temp above freezing. When they tried to tie the power supply to run only during defrost cycles, the pipe would freeze & burst. It had to stay on all the time since the box was always below freezing. The coldest box I remember was 10* below. Usually they were 0* or above.

We have run A/C condensate lines to a dishwasher style Wye under a sink. So the condensate ties in above the trap to avoid allowing sewer gases to travel into the A/C system. The condensate should have a 1/4" fall per foot like other drain lines. A couple of 90s don't seem to be a big issue. But you need to have access to blow thru the line if it ever clogs. Does this system use a second line for an overflow? Those are normally run to a location where water from them will be noticed, to indicate a there's problem with the primary drain.

In locations where the is not enough fall then the condensate pump is used. It seems like they last for several tears.

 

[zmaxmotorsports]

 

[sixty4]

Just did my 3 car garage and I am in a cold climate. I ran a 2" pvc line to the outside. I put it 18" off grade (for snow) and put a 45 on the end with a stainless bird screen inserted on the open end of the 45. On the inside I reduced to 3/4" pvc for coil and drain for hot air furnace. I made a condensate neutralizer as not to kill what grass I have behind the garage (and to make local code enforcement happy). The condensate from these things are really acidic. My garage is detached so no bathroom or waste lines to use.

 

[mires]

Robinson Tee above the trap on your sink drain.

Meets code in Texas but not sure about where you are. Or if you even care about that

 

[DC73]

Condensate pump and a piece of 3/8" copper tubing will take care of furnace and ac.

Would you run the copper tubing through the wall or up into the attic and then back down to the drain? Would the 10' high ceilings make a difference?

DC

 

[DC73]

Is heat tape an option?

Sure but I'd rather not have to worry about it or a condensate pump failing. A passive system would be best if I can figure it out.

We have run A/C condensate lines to a dishwasher style Wye under a sink. . . . The condensate should have a 1/4" fall per foot like other drain lines.

This would be my preferred method but it's a long way to the sink from the preferred furnace location (22' or so). If I relocate the furnace, I could end up within 12' of the toilet via the exterior wall. A 1/4" per foot requirement might be problematic with a standard installation. However, I will have 10' ceilings and could install the unit higher to give the needed fall. If I choose the right unit, I could even install it high on the ceiling in a horizontal configuration if I could get the AC and duct work figured out.

Does this system use a second line for an overflow? Those are normally run to a location where water from them will be noticed, to indicate a there's problem with the primary drain.

I could easily do this. Sounds like a good idea.

Thanks for the help.

DC

 

[DC73]

I made a condensate neutralizer as not to kill what grass I have behind the garage (and to make local code enforcement happy). The condensate from these things are really acidic.

Didn't realize the condensate was so acidic. Tell me more about how you made a condensate neutralizer.

If I go the dry well route, it's best location would be in reasonably close proximity to my ground rod, gas line and AC compressor. Wouldn't want an overly acidic dry well to cause corrosion issues. I could move it further away but may want to consider neutralizing the acid anyway.

Thanks,

DC

 

[DC73]

Robinson Tee above the trap on your sink drain.
Meets code in Texas but not sure about where you are. Or if you even care about that

I want a functional condensate drain that at least meets minimum code. Overkill is always an option with me.

DC

 

[big.jim]

Condensate pump and a piece of 3/8" copper tubing will take care of furnace and ac.

as mentioned condensate is acidic so should not be run in copper until it has been neutralised or diluted as it will eat through the copper , should be run in pvc solvent weld pipe

 

[zmaxmotorsports]

Would you run the copper tubing through the wall or up into the attic and then back down to the drain? Would the 10' high ceilings make a difference?

DC

Which ever is closer/looks better.

 

[BD1]

Check the furnace manual or with manufacture. Some high efficiency furnaces drain into a neutralizer container then go to the drain. It looks like a bunch of rocks in a shoe box.

 

[jvitez]

Since you'll have plumbing in the shop, use a condensate pump and run a line to a tee shown in mire's post. No worries about neutralization, it'll use very little electricity, and you won't have to worry about freezing.

A local British car shop I frequent (frequently, thank's to British engineering.....) has two new high efficiency hanging furnaces installed. Each uses a condensate pump exactly as shown in mire's post, run up to the ceiling with clear pvc hose, transitioned to rigid PVC pipe run the length of the shop to a drain. The owner says it's been no issue since installed.

 

[sixty4]

Didn't realize the condensate was so acidic. Tell me more about how you made a condensate neutralizer.

If I go the dry well route, it's best location would be in reasonably close proximity to my ground rod, gas line and AC compressor. Wouldn't want an overly acidic dry well to cause corrosion issues. I could move it further away but may want to consider neutralizing the acid anyway.

Thanks,

DC

Very easy to make. I used a piece of 3" clear pvc pipe about 1' long a 3" pvc glue cap on the bottom (that I drilled and tapped) for discharge. On top I used a 3" pvc female adapter and made the tap off the side that the discharge comes into it from unit. My plumping supply house carries the rocks that the use for the Peerless or Viseman boilers that have these on most condensate HW boilers (you can use marble chips to lower the PH). I was told 1" of the rocks in a 3" cylinder will do roughly 10,000 BTU's per inch in the cylinder. I have a valve on mine as I don't leave heat on as its a detached garage. Valve just drains any water when heat is off.

 

[DC73]

My plumping supply house carries the rocks that the use for the Peerless or Viseman boilers that have these on most condensate HW boilers (you can use marble chips to lower the PH).

How do you know when the rocks need to be replaced? Do they degrade over time and replacement is obvious? Or are they replaced based on a specific volume of water through them?

Thanks everyone for the comments. Appreciate the help.

DC

 

[RivennHewn]

I just installed a new furnace a couple weeks ago.

I lucked out. By pumping into a nearby floor drain, I avoided having to put a P-trap primer in.

Saved myself a few bucks.

 

[sixty4]

How do you know when the rocks need to be replaced? Do they degrade over time and replacement is obvious? Or are they replaced based on a specific volume of water through them?

Thanks everyone for the comments. Appreciate the help.

DC

Heating engineer told me every two years (somehow I have my doubts but will see over time). The inspector here that I spoke with before I started said make my own a lot cheaper and easier. I am going to get some PH test strips and test before and after the Neutralizer to see what it shows up as the next time I am at the supply house.

 

[big.jim]

crushed limestone is the rocks in the neutraliser ,it will wash away with the condensate so is obvious when it needs topping up , you wont replace because it washes away

 

[zmaxmotorsports]

as mentioned condensate is acidic so should not be run in copper until it has been neutralised or diluted as it will eat through the copper , should be run in pvc solvent weld pipe

Ive never had a problem with it yet anyway.

 

[BillK]

DC,
When we switched our house to gas heat about ten years ago, I used a condensate pump. It has a clear plastic tube that runs about 8 ft to the nearest outside wall and then into a 3/4" pvc line through the wall, down the outside about 12 inches deep into the ground and then under my gravel driveway and drains to the open air.

I have never had a problem with it freezing here in Maryland. It was 8 degrees a couple of nights a week ago and had no issues.

As far as copper pipe goes, if you are going to run it outside I would be concerned with the metal pipe getting cold and then possibly giving you a problem with freezing. You wont have that problem with pvc.

Hope this helps,

 

[roscoe2000]

Your condensate drain from the furnace will be on the acidic side (corrosive). So it would be best to use PVC for that run and be mindful of where you plan to drain it to.