Good evening everyone,

Probably not the best subject for my first post, but I've got to try and get my head wrapped around the debate over venting a laundry tray pump (Liberty 404, Zoeller, Saniflo...). I've read most of the posts here and elsewhere and it is clear that most agree on 2 things: The pumps CANNOT be vented with an AAV or one-way vent of any sort. Second, most state that they must be vented. I completely understand the wonderful concept of venting, really I do. In the case of the pump, the air in the pump has to go somewhere when the water from the utility sink wants to enter the pump. The vent gives it a place to go and the water flows freely into the pump. The vent also serves a critical role at discharge as well. The pump cant suck the water out if there is no air behind it. Got it. Where I'm falling behind is the insistence of some that it MUST vent outside and not just anywhere, but through the roof! Couple of things that leave me scratching my head. First, its not like there isn't enough air in the basement that the paint is going to be pulled off the walls if the vent is inside. Second, we're talking about a washing machine, not sewage. Third, I thought the whole idea of these magical pumps was to bring plumbing where you never imagined possible! What good is a completely contained plumbing system if you have to rebuild the house to get a vent up 2 stories and through your roof. I'll have $200 in a pump and $2000 to run a vent through the roof. Finally, I get the sense from combing through these posts that there are two solutions to the perplexing venting problem - the "code way" and, well the "not so code way." I respect code, the people who wrote them, and the plumbers that abided by them. But, I'm struggling to understand why it is imperative that these pumps be vented through the roof. Code aside for just a second, What is the worst that can happen if I vent this in the basement? I'll have a check valve with a union at the pump, perhaps one just before the wye joint where it discharges into the sanitary/sewer line, and a p-trap on the utility sink. Are we talking maybe a little odor, maybe? My plan for that was to put a 45 wye in the vent tube and dose it with a tablespoon of bleach or vinegar from time to time. If the problem persists, I run it out of the house. But, for gosh sakes, does it really have to go up two stories and out the roof?

I genuinely thank you for your time and consideration and apologize for beating this dead horse!

Mike

if you have a check valve on the outlet of the pump so no evil sewer gases can come back into your basement, as you said, the worst you will get is the smell of the tank itself.
i have seen a few just vented into the basement and the homeowners were not growing horns.

quote; Third, I thought the whole idea of these magical pumps was to bring plumbing where you never imagined possible!

1> That is NOT the "whole idea" of the pump. It is to make plumbing POSSIBLE, but not necessarily EASY.
2. If you sink does NOT have a "P" trap on it going into the pump basin, you do not need a vent.

Even WITHOUT a check valve odors would NOT enter the basement, because the pump's inlet will ALWAYS be under water, especially if the discharged water is continually reentering the basin because of the lack of a check valve.

Hi hj,

Could you clarify your note about not needing a vent if I DON'T use a p-trap.
I gather the idea of the trap is to prevent odors from existing the pump through the sink. If I'm venting in the basement the p-trap is pointless?
Thank You!

If you are basically using clear water the should either be no smell, or no air circulation to produce an odor, so you MIGHT be able to forego the "P" trap, and if you did that the open drain would serve as the vent.

All - Apparently I don't understand the "venting" concept as well as I thought I did! I'm not sure how the open drain (assuming no p-trap is used) would serve as a vent, or at least serve as a dual purpose vent. I've included a diagram of my proposed install and here is my understanding (and lack thereof as well) of how the vent is supposed to function. Air in the pump must have some place to go when the water enters from the utility tub. Correct? Venting the pump via the "vent port" on the pump will serve this purpose. Also, when water is leaving the pump, there is a need for air behind the water, otherwise the water will go no where. If this is accurate, how then can the sink drain serve as a vent in either of these roles? When water is entering the pump from the sink drain, air can't also exit the sink drain if it is full of water. Moreover, when the water is being discharged from the pump, the sink (and drain) will likely be full of water for most of the discharge. If that is the case, how can the pump draw air through a sink drain full of water? What am I missing here? Please forgive my ignorance.

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With the sink full and draining into the tray, the water coming into the tray will make up for the water being pumped out, volume for volume, and there is no need for any extra air.

Thank you, and that makes sense. So, one mystery left. An earlier post indicated that if I leave the p-trap off, the sink drain will serve as a vent. Related to this, where is the air to go from the pump when the water starts to enter it? It just hit me, there is only a small amount of time between that point where the water first enters and before the pump kicks on that we have to concern ourself with, right. Because once the pump starts pulling water in, were golden! So, p-trap or no p-trap. Not real sure it adds any value. Again, all help is appreciated.

Mike



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