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# Thread: How far can a vent run Horizontal

1. ## How far can a vent run Horizontal

I apologize if this is a stupid question, but I'm having trouble figuring out the answer from my books and code checks, so here goes:

How far can a vent run horizontal once it get up above your fixtures? For example in the attached picture:

1) as far as I can tell, Distance "X" needs to be <6 feet

2) For distance Y and Z, is there limitation before I turn up to the roof, or could I theoretically go across the house?

A little critic on my plumbing setup would be apprciated as well! Thanks,

FYI, I'm planning out a full basement bath and bar sink that is across the house from the main stack. I have another stack at the back of the house that I plan to run to, but I believe I need to run a new vent up the nearest wall to the new bath.... I don't think Seattle PLumbing code (UPC) allows side wall venting, which would have been easier.

Thanks again,
Nick

2. In my town, there is no length limitation on Y, Z. However, both sections must be downward sloping to the drain so that condensate any errant water that finds its way into the system has a place to go. There should be no low points.

3. Thanks for your help. One more follow-up question. Can I change direction on during that long horizontal run (either Y or Z in the previous picture) as long as I keep that 1/4 per foot drop for condensate?

I'm probably making more trouble for myself and ought to just run a new vent pipe, but fishing it up the interior wall is a real pain.

Thanks,
Nick

4. I think you'll find that once you are above the flood plane, as long as you have the slope to allow condensation or rain water from the roof to drain, it really doesn't matter where you go with it.

5. Ditto. Bend me, shape me, any way you want me. As long as you love me, baby, it's all right!

6. The X measurement with upc code would be from the vent to the flange,(six feet or less)

The vent horizontal could be 1/3 the vertical.

So if you had 24 feet of vertical, your horizontal could be 8 feet.
If you go up a pipe size, there is no limit.

7. I'm sorry, now I think I just got confused. Terry, did you just nix what the others were saying? Perhaps you could point me in the direction of the code far that horizontal vent code?

Thanks
Nick

8. Never mind, just found it... UPC 904.2... But it says:

"904.2 No more than one-third (1/3) of the total
permitted length, per Table 7-5, of any minimum
sized vent shall be installed in a horizontal position.

Exception: When a minimum sized vent is
increased one (1) pipe size for its entire length,
the maximum length limitation does not apply."

Am I mis-reading? This appears to say that it is allowed to be 1/3 the TOTAL length, which for a 2" vent would be 1/3 of 120 feet, or 40 feet.

9. That's how it appears to read.

1/3 of total allowed. That would mean that up to 40 feet of 2" could be horizontal without going up a pipe size.

I wish I had seen that 10 years ago when I was doing a resturant in Bellevue. The inspector didn't see it that way.

One third of the allowed lenth is much more than 1/3 of vertical.

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