Drain unclogged, now a backup problem

[blues1360]

So my drain cleared out, believe it or not. (I had a stubborn drain in a cement slab, that I will be using for a shower, see post from yesterday on clogged drain in slab) I can pour water rapidly and freely down the drain. So a new problem... My washing machine is hooked up to the same waste/vent pipe. The machine dump is above that of where my floor drain enters the line. When my machine dumps its water from the cycle it starts to back up in the floor drain. This time it came just about out of the drain, then receeded. My question... what causes this and how do you fix it? Drain woking well now, just need to fix back flow problem. FYI when I am done leveling the floor etc. my drain hole will be a few inches higher than it is now. Thanks again, this forum is great!

[Gary Swart]

One of two possibilities. First, the drain isn't as clear as you think, and two, the drain is too small. You were asked in your previous thread what size the drain is, but you didn't answer that question. Newer washers dump so much water so fast that it takes a 2" drain to handle it. A shower requires a 2" drain also. You should be aware that you can't go from a larger size pipe to a smaller one. You can only increase the pipe size as you go toward to outlet end. If that 3' section for pipe going to the main drain is only 1-1/2", that's your problem. You may still have to open the floor.

[plumber1]

The drain didn't clear out. You put enough water down it and it goes away, so what? If you are going to do anything positive, get a good, not a Mickey Mouse, snake and you should be able to clean that sewer and and it should accept your discharge from the washer.

[blues1360]

My drain is a 2" drain, at least the one for the shower. That I am positive of. In terms of the wahing machine drain, Im not sure. What causes the water to back up?
I'm not saying that I know what I am talking about...now what I am saying is that I have put a bunch (25 galllons) of water down my shower drain as fast as I can pour (5- 5 gallon buckets) and the drain sucks the water down as fast as any drain I have ever seen. Since the drain is the right size... Does that mean I should call a plumber and have them snake the drain to fix the backup problem? Can I do it myself? Question 2... If my washing machine drain is 1 1/2" will increasing it to 2" help?

[Gary Swart]

Do what you have to in order to get the drain completely cleaned out. If it's only a 3 foot section it shouldn't be that difficult. The shower has the proper size drain, so it will handle all you can dump into it, and that's really the answer to Question #2. If you do not increase the washer drain to 2", you will almost certainly continue to have problems. As I stated in my previous post, newer washers dump the water at an astounding rate, and a 1-1/2" standpipe/drain just will not take the volume of water fast enough. But, you can't start at the washer with a 2" pipe then drop to 1-1/2", it needs to be 2" until it joins a 3" or 4" line.

[blues1360]

Thank you very much for the advice. I will check the size of the drain attached to the washing machine discharge hose. If it is 1 1/2 " I will increase the size to 2". Otherwise I will get the floor drain cleaned out. My thoughts... I will continue to work on the drain with a hand snake. Meanwhile intermittently checking the drain by using the washing machine. My presumption is that if the backflow is caused by the drain being partially clear, when the drain is clear there will be no backflow. (I am nervous for saying that because presuming makes an a_s out of you and me)
If I can NOT get the backup to stop, I will rent an larger snake to clear the drain. Two questions... Does that sound reasonable? And... Why if the drain is not totally clear does that cause backflow from the washing machine?
I can easily follow the advice given here, and plan too. I just want to understand what is actually going on here. Thanks a bunch.

[hj]

Even a 2" drain line, if it goes horizontally for a considerable distance will fill with water from a clothers washer. If the line is fairly close to the floor level, with minimum vertical drop, the water will back up into the drain, and if that is the problem there is little that can be done to correct it at this point.

[Mikey]

IPC SECTION 406
AUTOMATIC CLOTHES WASHERS

406.3 Waste connection. The waste from an automatic clothes washer shall discharge through an air break into a standpipe in accordance with Section 802.4 or into a laundry sink. The trap and fixture drain for an automatic clothes washer standpipe shall be a minimum of 2 inches (51 mm) in diameter. The automatic clothes washer fixture drain shall connect to a branch drain or drainage stack a minimum of 3 inches (76 mm) in diameter.

802.4 Standpipes.

Standpipes shall be individually trapped. Standpipes shall extend a minimum of 18 inches (457mm) and a maximum of 42 inches (1066mm) above the trap. Access shall be provided to all standpipe traps and drains for rodding. No P-trap for a washing machine standpipe shall be installed below the floor.