Plumbing Question: Slow draining urinals?

Question

My business has a bank of 5 urinals. For a number of years we've had a problem where urinal #1 and urinal #2 do not drain properly. On both I have to turn the water pressure down considerably so water doesn't fill too fast, and even then I'm lucky if they don't spill over before the water stops flowing. This problem does not exist in urinals #3 - #5.

The urinals have been pulled from the wall many times to have the line snaked, and we use an enzyme treatment regularly.

At one point we changed out the urinals to a new design, and that still did not resolve the problem.

Any thoughts on what might be causing these urinals to not flush properly when there is no obstruction in the line?

To the best of my knowledge, all 5 urinals flow into a common line which terminates by #1 and flows to the main line by #5.

mustanger · Accepted Answer

For water to flow out the line has to be vented. If you have it chacked out I'll bet that the vent pipe is down by #5. That means #5 will flow the quickest as air leaves easily. As you move back up the line each will drain a bit more slowly and by the time you get to #1 & #2 they drain so sowly they tend to overflow. The smart thing would have been to vent in the middle when it was installed. A plumber can cut into the wall and install a vent between 1&2 and solve the problem.

Anonymous · Answer

There's a saying "You can't fit a quart in a pint pot." If you have eliminated a physical blockage as the cause, then the cause is probably lack of capacity for flow.
Consider the case where you had 3 urinals and the outflow from urinal 1 joins the outflow of 2, then a bit further along joins urinal 3. 
What if the flush was on all the time, each pipe could only carry exactly the amount of water provided by the flush, each pipe (and the final outflow) were the same size?
You will obviously get overflow because there is not enough capacity to remove the water.
Probably, you need to step size the pipework up us you join each urinal and at the outflow. Not necessarily doubling the size, because I presume they do not all flush at the same time and you will have spare volume capacity.

chris · Answer

Since you numbered them, I would assume that 1 & 2 are the closest to the door and get used more than the rest. It is very common for calcium to build up in the traps of heavily used urinals. I use Muriatic Acid and let it sit in the trap for a about 1 - 2 hours to dissolve the build up and then it works fine for months. There are other acids you can get from plumbing supplies to do this, but muriatic acid is cheap and easy to get at Home Depot or Lowes. Just make sure you barrier off that urinal when using it for obvious reasons.

Also, snakes won't cut through calcium, you almost need a hammer and chisel. (or dissolve it)

John · Answer

Plumbing services in Chicago call +1 312-544-9150

? · Answer

put a larger trap in 4 and 5 very cheap  and easy takes 5 mins

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Plumbing Question: Slow draining urinals?

5 Answers