Tying into existing drain line - Venting question

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Patflemming

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I am trying into a bath and lav drain line and installing a diverter valve to allow me to choose between sending water towards the sewer or to my grey water system.

I want to make sure I am choosing the proper location to tie into. I'm thinking of installing the valve after the bath/shower and lav drain lines combine. I am correct in assuming that this location would be vented?

grey water.png
 

wwhitney

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So starting at the lavatory drain, first it hits the bath drain, then the combined drain hits the toilet drain? With the lavatory drain being dry vented, that is the usual way for a lavatory to wet vent a tub and toilet.

In which case if you put your diverter valve at the indicated location, the tub will be vented with the valve in either position. But unless your toilet has a separate dry vent on it, your toilet will no longer be vented when the diverter valve is going to the grey water system.

Note these are just my initial thoughts--I have no experience with grey water systems or diverter valves.

Cheers, Wayne
 

Patflemming

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So starting at the lavatory drain, first it hits the bath drain, then the combined drain hits the toilet drain? With the lavatory drain being dry vented, that is the usual way for a lavatory to wet vent a tub and toilet.

In which case if you put your diverter valve at the indicated location, the tub will be vented with the valve in either position. But unless your toilet has a separate dry vent on it, your toilet will no longer be vented when the diverter valve is going to the grey water system.

Note these are just my initial thoughts--I have no experience with grey water systems or diverter valves.

Cheers, Wayne
Very good point! I guess you're right, the toilet wouldn't be vented when the valve is turned towards the grey water drain.

What if I plumb it like the image below. Even when the valve is open to direct water to the grey water system, air would still be able to reach the toilet drain line. Does this make sense?

The tee will be positioned so it's a vertical drop to the valve.

1704413122439.png
 
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John Gayewski

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Very good point! I guess you're right, the toilet wouldn't be vented when the valve is turned towards the grey water drain.

What if I plumb it like the image below. Even when the valve is open to direct water to the grey water system, air would still be able to reach the toilet drain line. Does this make sense?

The tee will be positioned so it's a vertical drop to the valve.

View attachment 96312
How do you stop water from going to the sewer? You'd need another valve, but then your toilet is directly connected (although up stream) to your grey water tank.

I'm not sure any of this is legal, have to checked with a local ahj to consult on this?
 

wwhitney

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When the valve is open, your grey water system would be exposed to any sewer gases from the sewer system. Not sure if that's OK or not.

Seems like you are trying to reinvent the wheel here. Surely there is some design guidance available for grey water systems? The simplest solution (design-wise, not necessarily execution-wise) would be to add a dry vent for your WC.

If you were plumbing a whole house for grey water from scratch, then I would think you would effectively install two separate DWV systems, one black and one grey, with independent venting, and then combine the two outputs very close to the actual building sewer, with a diverter valve for the grey water system. So from that point of view, separately dry venting the WC is the way to go.

Cheers, Wayne
 

John Gayewski

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At the 20:00 mark, it recommends to install a diverter valve down stream from the vent but before the black water.
Right, but that's not what your doing. Your installing it in the toilet vent which is a wet vent.

At the 19 min mark they also say your gonna wanna hire a plumber if you need to reconfigure your plumbing.

Your proposition with a tee pointing straight down in not gonna be something an inspector would sign off on if I had to guess.
 
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