I have two floor drains upstairs, one in the laundry room, and one by the water heater. Both have p-traps, but because these drains are only used in the case of a broken appliance flooding, the water in the p traps evaporates, letting sewer gas in. The drain by the water heater experiences quicker evaporation due to the heat from the furnace and water heater. Would a back-flow preventer prevent the back flow of sewer gas? Should there be s-traps instead of p-traps?

 

No and No

Your just going to have to add water on a routine basis

 

Since I posted my question, I ran across a website for Danjer. They claim to have a floor drain insert that does the trick. What do you think? I'm a very forgetful type, and I'm afraid I won't remember to add water until the gas is in the house and giving us all headaches.

Or what about adding RV antifreeze to the trap. You know the pink antifreeze that people use to winterize their summer cottage? Would that evaporate slower? I guess I'm hoping you are a chemist as well. I think that it is propylene glycol...

 

you can put a little mineral spirits in there and that should stop the evaporation.

 

Don't pour anything flammable into your drain by the water heater.

I'm sure Winslow meant Mineral oil.

Vegetable oil is not used as it will putriefy in the dran and smell very funky in a few days.
The little backwater blocker will not stop sewer gas. The ones I've seen are like little ping-pong balls in a cage like thing. Great for water rising, doen't do anything for your sewer gas due to a dry trap.

 

And..............

If you want to never have to worry about sewer gases again, of course you will have to do alot of work, to include opening up ceilings and replace the plumbing at the trap, you could install primers, primers add a drop of water so often to the traps, allowing them to keep there seal.

 

So you too are the forgetful type -- was that mineral SPIRITS or mineral OIL?

Like Ron said in his 1st response, you are going to have to add a little water to the drains on a regular basis. So, on the first of every month, when you change the calander, pour a quart of water down each drain. Or, better yet, every payday, dump a quart of water down each drain. Or, another way -- while you are waiting for the coffee pot to brew the first pot every morning, go pour a cup of water down each drain. Like me, you manage to get home (to the same house even) every nite after work -- you can't be THAT forgetful!!

 

thank goodness there is safety in numbers!

 

Thank you all so much. Your advice is in action as we speak.

 

Really, since both of the drains are in the room with local plumbing it would not be hard to install trap primers... they could be cut in on the water to the heater and the washer,... little bit of work, but you wouldn't necessarily have to run them under the drywall or anything... but otherwise some kind of schedule is in order... Of course, you can also just cap them off and take a chance on NEVER have a flood problem upstairs but this is not highly recommended... but just an idea, where is your furnace/ac unit in relation to these two traps? any chance of running one of your condensation lines to either of these floor drains?

 

Of course Ragnar, one could run a pipe to the floor drain on top of the floor, but, who wants to see a pipe stuck out in the floor and having to step over the pipe to get to where there going, you know some don't watch where there going and could very easily trip over the pipe.

Safty 1st is how I look at things.