If you are doing some remodeling work and noticed that the vanity in most cases has a shelf with drawers that are high near the drain pipe. Which means it leaves little room for putting in the drain pipe.
Your options are limited in this case and the p trap could end up higher than the drain pipe. However, ideally a p trap cannot be higher than a drain pipe as it will not serve its purpose as intended.
In this article we will cover reasons why a p trap cannot be higher than drain pipe and what you can do to fix the problem and avoid future problems.
Can P Trap Be Higher than Drain Pipe
As we have stated a p trap cannot be higher than the drain pipe. A p trap is a device where the output level is higher than the input level. Which means water flows in and is then trapped creating a seal to block harmful gasses from traveling upwards to the sink.
Therefore it means that the p trap works with gravity where the water goes downwards naturally. Unless you are planning to pump the fluid upwards then the p trap will not be able to create a seal and you are highly likely to smell some methane gas in the room.
When doing an installation the location of the drain is not as important. It can flow downwards or outwards just not higher.
Fixing a p-trap higher than the drain pipe creates an S-trap which could make it siphon and let sewer gas in your house. Besides making your home smelly, some of these gasses are poisonous and explosive.
Moreover, S-traps are illegal in all the 50 States, the United States and other countries today because they let sewer gasses into homes and other external conditions.
This is because when a nearby toilet flushes the force will cause a suction and remove some of the water, removing the water seal and allowing methane gas in.
What Do I Do If My P Trap is Too High
If this is a vanity you are installing and the drawers are leaving little room for a p trap to be installed. You will have to cut through the drawers to create space for the p trap to be installed.
The second option is to remove that particular vanity drawer so as to create room to extend the tailpiece in to allow you to put in the p trap correctly.
In the last resort you will have to knock down the wall to reroute the drain pipe in the wall to have it in line so that you can install the p trap properly.
See also Can A P Trap Go Either Way?
How Far Should the Sink Drain Pipe Go Into the P Trap
The International Residential Code stipulates that the most vertical distance there can be between the entry to the p-trap and the sink drain is 24 inches. However, on the other hand, according to the Universal Plumbing Code, you must maintain a developed length of 24” or less for the fittings, arms, and tailpieces joining your p-trap to the sink drain.
The p-trap must be lower than the drain from your sink basin and can also sit lower than the exit pipe. Moreover, make sure you don’t have your p-trap lower than the exit drain because that will interfere with the water’s natural flow, so the water gravity will have to force it out.
Does the Height of the P Trap Matter
The height of the p trap does matter, because if it is too low then it leaves a higher distance that will allow evaporation of the water in the trap.
Therefore Universal Plumbing Code states that the p trap height should be between 6 inches 18 inches above the floor level. This height allows for repairs easily and allows for proper working of the p trap.
FAQs on P Trap Higher than Drain Pipe
Does a Vent Need to be Higher than P Trap
The vent should always be higher than the p trap so that you ensure balance of pressures on both sides of the p trap. In addition, it prevents siphoning of both air and the water in the p trap.
Can a Vent be Below A Trap
You cannot have a vent below a trap except for water closets as they have their own p traps.
Does Every Trap Need a Vent
Yes all p traps need a vent through which they will release the pressure in the sewer line and avoid bursting of pipes.
See also How Deep Can A P trap Be?
Whether installing a p-trap for the first time or replacing it, make sure you do it properly for the best functionality.
The p trap cannot be higher than the drain pipe because in such a set up there will be no water trap seal. Which means that gasses from your sewer such as methane, carbon monoxide and hydrogen-sulfide will find their way into your home.
Therefore, you must fix the problem and make sure that the p trap does not go higher than the drain pipe.
See also How Much Room Does A P trap Need?