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Old 02-10-2008, 05:16 AM   #1
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P-trap advice

As many of you may know, I'm always worried about freeze problems. The traps are a particular problem, since I add a little anti-freeze in each one each night, which is a royal pain. My question is, what would be wrong with one trap? Right now my Safari has three, arranged something like the upper diagram here:

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The lower diagram is what I would like to go to (ignore the red line on the tank for now). There is plenty of room to put a trap near the inlet of the gray tank, plus this area is deeper than the rest of the belly, allowing the trap to be completely inside. I don't like the current shower trap--it projects beneath the belly pan and has its own bump-out cover. When you remove the cover, there really isn't any room to do maintenance on the trap or any other plumbing, so it doesn't seem to be a very useful bump-out.

Another advantage of the lower diagram is that it's self-venting. The upper diagram would show two vent lines, if I had included them (actually, 3, but one of them is a vacuum breaker vent right next to the sink). This seems excessive and I want to get rid of all but one vent if I can.

The second question I have is, what if the gray tank is made larger, so that it's right up against the floor (the red line)? Obviously, the drain line under the floor could wind up with gray waste water in it, either from traveling slosh or when the tank is near full. Would this present a big odor problem? (I intend to prevent slosh into the shower pan with a drain fitting that will accept a screw-in plug.)

Any better ideas out there? The current gray tank holds maybe 10 gallons max, so it's not acceptible to me. I can make a tank that is twice as big and still maintain about 1-1/2" clearance below the floor, but this is cutting is close for keeping the upstream drain lines from the trap clear.


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Old 02-10-2008, 06:03 AM   #2
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With "long" runs of pipe and no trap at the business ends - are you not concerned about odor from the slime that will build up in the lines over time. I've seen that for example where someone installed a laundry tub in a basement and "T'd" into the trap at the main connection rather than installing one right under the sink itself.....

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Old 02-10-2008, 06:49 AM   #3
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The vents (air admittance valve) on the system provide protection from siphoning of the trap or traps. You should have the trap in close proximity of the drain to "seal" the order's and bugs from accumulating in the UN trapped portions of the pipe. The running trap you show in your diagram is likely to be vulnerable to siphoning and allows for to much piping to accumulate the slime that "ganglin" is referring to.
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Old 02-10-2008, 07:10 AM   #4
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At a minimum, you would need to add a vent after the p-trap as stated above to prevent the trap water from being sucked out.


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Old 02-10-2008, 09:43 AM   #5
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Thanks all. It was early, is why I was thinking the vent on the wrong side of the traps.

Slime. hmmmm. Hadn't thought of that. Maybe there is a good reason for the current design... I was thinking that the real odor problem came from the festering water in the tank. Then again, there's always a good dose of Clorox now and then!

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