P-Trap Drain Not Draining Issue

I have a p-trap drain in my restaurant that isn't draining, when we disconnected the dishwasher drain hose water sprayed out of the drain end like it was under pressure. The dishwasher had not been run for over a week. I have taken the trap apart, snaked it out. I have also snaked all the other lines of this system yet the drain just fills with water. I don't believe any water is leaving through this p-trap, the water will over flow over the top of the drain line if I continued pouring water. I will attach a picture I think the issue is someone has tied this "drain" into a vent line. I have a two vent pipes in the sink area (very close together), one on the other side of the wall before the grease trap and one after the grease trap before the exit to the sewer. ant suggestions? Thanks!

The drain is plugged and you will need to call someone with the right equipment

Have you checked to see if the grease trap is allowing water in?
It may be time to clean it.

"Connecting to a vent" if it is installed properly, does NOT cause drainage problems. you have a drain line stoppage. I hope the dishwasher drain line is not "connected" to the system without an |"air gap", so that any "backflow water" could contaminate the dishes.

Terry said:

Have you checked to see if the grease trap is allowing water in?
It may be time to clean it.

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Yes the grease trap is open, I have 2 dishwashing sinks and one hand washing sink that goes to the trap with no issues. So only place a blockage could be is at the bottom of the pipe shown on the left, yet all the other sinks drain through the main also...

The drain pipe is much more then just at the bottom it will run out 5,10, or more feet and any or all of it could be clogged with grease and that is why you need a professional drain person to clear the drain !

MACPLUMB 777 said:

The drain pipe is much more then just at the bottom it will run out 5,10, or more feet and any or all of it could be clogged with grease and that is why you need a professional drain person to clear the drain !

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This p-trap drain line is after my sinks, before my grease trap yet all the sinks drain with NO issue. So if a clog is present it has to be at the bottom of the line shown on the left, which is about 12-18" long?

The clog is likely right there in one of the bends in the line .

I would cut out a section of the vertical vent line and rod the drain, and then install a cleanout where I cut the line for the next time it needs to be done.

cacher_chick said:

The clog is likely right there in one of the bends in the line .

I would cut out a section of the vertical vent line and rod the drain, and then install a cleanout where I cut the line for the next time it needs to be done.

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I'm in the process of doing this, having a hard time finding 1 1/2 PVC Fittings here, can I use ABS if its only for the vent line? No water flow. I have cleaned my grease trap and it was quite bad so I bet there is a clog at the bottom of the line.

There is a special transitional cement for bonding PVC to ABS. I would look harder for the PVC fittings first.

If you want to do some trading, I could use a couple of ABS continuous waste with end outlet kits. ABS is quite uncommon here.

I found the PVC fittings, had to call the local pluming store (One Stop Plumbing).
I found there was a clog in the bottom of the line, and this is why the p-trap wasn't draining. I was able to free it up using my snake, and I also got good drain cleaner and put it down all my drains.

Thanks for all the suggestions everyone, much appreciated. I will now keep an eye on the grease trap and maintain it.