My house is 24 years old; I have lived here 16 years. The furnace is a 95%
about 5 years old. There is an A/C also. The humidifier also drains to it.
Two years ago there was water on the floor next to my furnace. The repair
man said that the condensate drain was clogged; he blew it open with
This year the man cleaning my furnace said the drain was slow and he blew
the drain open. He said it was likely to clog and recommended I install a
The condensate drain goes into the floor. There is a bathroom with a drain
in the concrete floor on the opposite side of the wall from the condensate
drain. I presume the condensate drain plumbs into the bathroom drain, but I
don't know that; it could just go into the space beneath the floor.
I asked the guy why it was clogging, but he didn't know. I asked him if
draino would be worthwhile; he said it couldn't hurt.
So, my questions...
1) Why would the drain be clogging after being fine for 20 years? In fact,
why would it clog at all? Isn't condensate just water?
2) A fitting inside the furnace has clogged twice also; the guy says they
designed it too small and it is subject to clogging if not cleaned
regularly. Clogged with what?
2) Would draino be a good try? (In the drain, not the furnace!)
3) Wouldn't a condensate pump be just as likely to clog as a condensate
I have blown out condensate drain lines that would partially clear, but
could tell they were still restricted. Took the lines apart and found
the lines full of semi solid crud with about a 1/4" hole in the crud.
You can blow them from now till doomsday and never get them clear.
Sometimes they can be taken apart and rodded out or replaced. My
experience with Liquid Plumber/ Drano is that you could use liquid dish
soap and get about the same results--none. I have used professional type
drain opener from HD and Lowes --at about $10/bottle--- with good
results. The company I'm with likes to install pumps, but I personally
use them as a last resort only. FWIW, I'm talking about a/c drains
only-- there are probably not a dozen condensing furnaces or humidifiers
Did anyone take the time to look for the drain termination? Sometimes
instead of draining into the sewer, they will terminate outdoors in the
flower bed next to the residence. Walk around the house and see if leaves
and other obstructions haven't clogged the end of the drain pipe. Sometimes
landscapers will redo the flower bed and overfill the area clogging the
drain. Sometimes homeowners will pour a new patio slab and cover over the
drain not knowing what it was for. A little checking can go a long way.
A condensate pump is nice.......................if you need it. In
reality, it is another device that will eventually clog, leak or
break. On condensing furnaces, I flush them out with hot water on
every winter check up. Usually about two gallons right through the
secondary and the condensate trap. They do get clogged with shit. Flue
by products and condensate create crud, plain and simple. It has to be
flushed. Your under floor drain is the same way. Put a tee with a
short pipe and cap somewhere in the condensate line (NOT in the
furnace). Every month pull the cap off, insert a funnel and dump a
gallon or so of hot water through it flushing all of your condensate
lines all the way to where it exits under the floor or at the floor
drain? After that, pour a few ounces of bleach through it. (Again, NOT
through the furnace condensate passages). Very little work for a clean
running drain. Remember, dark and damp (as inside a drain) are great
conditions for growing slime, mold and collecting crud. Flush it,
Flush it, Flush it.
That is how I felt; adding a mechanical device when gravity will do can't be
Actually the drain is already open. The drain line goes up vertically; the
furnace and humidifier go down and then horizontally to Ts on the drain
line. The drain line is open at the top, so I can just pour the hot water
in there. Unless it is completely clogged (which I know about because the
furnace stops) it will not affect the furnace.
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