Possible to waterproof a basement furnace room?

Factual Questions
1

We have a storage room in the basement that houses our HVAC unit. Two or three times the floor drain or the condensate line has clogged, causing condensate to puddle on the floor. There is a floor water detector that shuts off the A/C but by then the water seeps under the framing into the carpet of the main room. It seeps in from the padding on up; very difficult to get it dry befor it mildews.

Is there a way to seal this storage room off from the living space so that small amounts of water cannot penetrate? It has a concrete floor with conventional 2 x 4 framing and drywall. I thought of something like plexiglass 2" high sealed to the floor with the same silicone sealant they use in aquarium tanks. But I figured I’m not the first one to need this so maybe there is an industry standard approach. I need to seal a portion of the perimeter that is about 12 feet long.

2

I think you need a shower pan liner. Like this:

http://m.dixsystems.com/?url=http%3A%2F%2Fwww.dixsystems.com%2Fsecond-floor-laundry-shower-pan-liner&utm_referrer=#3127

3

Moderator Note

Thread title fixed.

4

What ZipperJJ said is easiest most likely.

Otherwise, what you are asking about is really best done during initial construction. Planing the floor so that it all angles down to the drain, a raised concrete “bulkhead” under the walls to contain leakage etc. are things I’ve seen in basement utility/mechanical rooms and are all still feasible in an engineering sort of way, but other factors such as cost and complexity of the project may negate that. You could add a rather thick bead of silicone to the base plate (2x4) of the wall around the perimeter and add a raised threshold to the door with silicone caulking as well I suppose. Not sure how effective it would be against any water deeper than 1/4 inch though. also, you might put concrete backer board inside the room on the walls instead of drywall and silicone that to the floor.

5

Personally, I’d start by dealing with the problem instead of putting a (complex) bandaid on the solution.
If the condensate line is clear, it should be easy to keep an eye on it. Check it every few months for red or black growth and when you see it, pour a bit of bleach in there or even see if you can fish a wire though it. In a pinch (if it T’s up at the top) you can blow into it, that usually clears the blockage, at least for now. Another solution (though it may just buy you some time) would be to get an adapter to step it up to a larger tube/pipe. I’ve also heard it said that a black tube, instead of a clear one, inhibits mold growth, but IME, that’s not always true and just makes it harder to clean.

This is also assuming that the blockage is in the tube, not the AC condensate drain pan. I believe they also make some kind of tablets that you can drop into the pan to help deal with this, but it does take a bit of know-how to gain access to it.

Another option is to just set a schedule, say, every 6 months/once per cooing season and replace the line.

As for a something to put around it, they do make ones, specifically for it. Google ‘water heater pan’ or ‘furnace drip pan’. It’s a pan that goes under the furnace and and has it’s own drain port that you’d run a line from to your floor drain. It’s meant specifically for this problem.* It might be difficult to install since furnaces don’t have a lot of wiggle room since they’re screwed into the plenum. IMO, if you don’t want to move/lift the furnace, I’d figure out where the high side is going to be, cut that side, slide it under and caulk it back in place.

So, yes, there are some options out there for you.

*These are usually used in attic installations and, to go a step further, the drain from this pan should be routed to a different location than the drain from the actual AC so if one clogs and overflows, the other one isn’t clogged as well. For example, if you have one running into a plumbed drain, you’d have the other one going out a sidewall and dripping outside. In your case, this isn’t as much of a concern. They can both run to the same drain, just don’t connect them to one line (like, with a T connector), each one should have it’s own individual run to the drain.

6

I am with Joey P here; lets fix the cause rather than trying to waterproof a room.

There has to be an issue with both the floor drain and condensate line. The floor drain should not be clogging. Get it looked at and properly cleared. Identify what is causing the clogs.

As far as waterproofing the wall, if you still must go this route I would look at either a brush on waterproofing product like Ardex 8+9, or installing a waterproofing membrane like Schluter Kerdi or Ditra (or their equivalent). These are all tile substrate products so will bond well with drywall, wood and cement. You will need to prep the surfaces being sealed to eliminate gaps and holes. The Ardex is the simplest and you can turn a plywood box into a bathtub with that stuff.

7

Hmm…Maybe we need tablets but there’s no easy way to put them in the evaporator A-coil. Our drain has clogged a couple of time and caused a puddle. As a solution I made an adapter to connect a garden hose to the drain and flush with full pressure flow about once a year.

3X on fix the problem! How does the water get out of the basement now? If it uses a small pump reservoir it would be possible to parallel two of these units so that at least one of pumps should be working.

8

Thanks for all replies thus far. This is great feedback but let me add more info.

A shower pan liner will not work. This is for an HVAC unit, not a shower or clothes washer. It is not practical to place the entire unit into a pan. And part of the problem is the drain itself clogging. A pan doesn’t help if it can’t drain. (I have a pan liner under my washing machine, which is on the second floor, and it has a drain pipe to drain out any spilled water. The first and only time it ever went into action, I discovered that the home builder had not properly sealed the drain pipe to the pan and water drained outside the pipe and ruined my living room ceiling.)

I agree that the root cause should be addressed, but I need a risk mitigation in place for when primary measures fail.

Last week, the condensate line clogged from the accumulation of crap in the trap. (I don’t know how condensation contains enough impurities to clog a trap but apparently this is quite normal.) The line backed up into the inside of the unit, and water was leaking out of the joints of the unit. It is a straightforward matter to clean the trap, as seen in this video with the same type of trap I have. So simple preventive maintenance is in order.

Second, the condensate line drains into a hole in the floor that goes into the sump. This hole has clogged two or three times since I’ve lived in the house (20 years). It is rare but is a huge mess when it happens. When this happened I suctioned it out with a wet/dry vac. Once I had to suction, then pour more water in to try to loosen the clog, which was successful after 2-3 repetitions. However, access is very difficult because the drain hole is underneath the main duct from the air return duct into the blower, with only a couple of inches of clearance to work with. (One of several bits of shoddy work by the builder.) One time it was blocked by a wooden disc that had been cut by the builder out of the joist to make a path for the electrical wiring. The disc was just the perfect size to plug it up. Another time I got a dead mouse. Another time it was just a bunch of generic nasty stuff.

So I am not sure how to prevent the drain from clogging, aside from suctioning it regularly as a preventive measure.

I just want to have a backup plan since this can happen any time of day or night without the HVAC bothering to call or text me to let me know it’s happening. FluffyBob’s suggestions seem very feasible. I am not looking to make my basement swimming-pool worthy, just mostly buy me time so my carpet doesn’t get ruined if there is a breach.

I’ll try to post some photos when I get home.

9

Well, as I mentioned before, you have to figure out of the problem is in the a-frame pan or in the tube (where it usually is). If it’s in the tube, it might just be right at the drain port and you can just unscrew the drain and poke at it to knock it loose or grab it with a needle nose pliers. If you really want to get a tablet in there, I can think of few ideas. An easy one would be if you had a vent in your plenum directly above the AC, to condition that room. You could just toss it right in there. It might even be easy enough to unscrew one of the ducts that connect to it. The “right” way is to open up the plenum access panel. There’s usually a sheet metal panel attached with a handful of zip screws. Just take off enough of them that you can drop the tablet in. The last thing I can think of is to just punch a hole (maybe a series of holes with a drill) big enough to slide it in, in the plenum, drop it in, the seal it shut. Then you can do this whenever you need to. But be really careful with this method. Stab something in to far and you’ll need the AC replaced/patched and recharged.

Having said all that IME, the clog is typically just mold/mildew in the poly tubing condensate drain line. Dump some bleach down it, jam a wire in it, blow throw it, replace it. Something, it’s not usually that hard.

10

Without knowing the setup of your basement, can you bypass the ‘underground’ line and just run the tube straight to the drain. I see that’s the problem, not the actual floor drain itself.

If you have a utility sink nearby, you can get a condensate pump and just run a line up that. They’re not too expensive but they can break down (not that often, every every couple of years, maybe) so I’d have some kind of back up in place. Even if it’s just a moisture alarm on the floor.