Trap question

I have problem with standpipe trap. Unfortunately, sanitary tee the standpipe is connected to is just 4" below the stand pipe top. My question is can I lower the trap adding a section between the trap curve and 90 degrees elbow. Thus I could maintain proper standpipe height and drain it to the main sewer.
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Alexander Galkin wrote:

Like this??
| | | |STANDPIPE |TEE | |+------ --------| | | |TRAP | |__| |
Now, you want to lower the "U" part of the trap by adding length to its left leg? That will work OK. It will mean that there is more water in the trap (deeper trap seal). The standpipe top will need to remain above the trap outlet to the TEE.
Jim
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I understand. What's the minimum height of the standpipe relative to the tee level?

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Alexander Galkin wrote:

As long as the top of the standpipe is above the TEE, it will work. If this is for a washing machine, where there is a lot of water flow, you want the standpipe to be as high as possible to prevent overflow. Jim

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I read in a plumbing book that NPC states that standpipes must be between 16" and 48". Does this mean the it must be at least 16" above tee level?

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Alexander Galkin wrote:

I would think the 16" refers to height above floor. Jim

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