ticki2 - this quote goes way back, but I'd like to get your thoughts on a couple of things you bring up here.
ticki2 wrote:
Dave , I can relate to how you think your way through a process . If I become annoying with comments just tell me to back off .
I have not had good luck with the nut and washer type traps that you show for the shower . They tend to loosen with vibration . If you want the flexibility of taking apart without cutting a fernco fitting works better . I also don't think it's a good idea to reduce down for a shower . I didn't read any mention of a vent for the grey tank .
With the shower drain and top of the grey tank being so close in elevation I will be interested to hear if there is any back up into the shower driving with a full grey tank . I have a similar situation and have not come to a resolve yet .
Fernco Trap: Using one of these instead of the nut and plastic washer still leaves a nut and washer for the downstream connection to the plumbing, what do they call that? A wall adapter? At the residential rough-in location? How do you deal with that? One idea I'm having is to NOT use a Fernco Trap, but instead, a glued trap that uses a Fernco coupler at both up and downstream connections, eliminating all nuts and washer.
Reducing down to 1.25": I appreciate those comments, but one thought is - that reduction might not matter TOO much in a short distance with a minimal water use flow, but MIGHT aid in the "slosh back" with a full tank?
Slosh Back: Do you think the combo of both a trap (1.5" p-trap even a waterless trap as you've suggested too - which uses a flapper valve apparently) and an o-ring sealing tub/shower stopper might control this?
Grey Tank Vent: The tank is vented. It's downstream of the galley sink trap, so that should work well. The bath sink is also vented, but upstream of the bath sink trap so that will aid the basin, but not other fixtures. Do you think the first vent described will aid the shower drain? I'm thinking yes, but maybe haven't thought it through fully.
Minimal Drain Elevation: There is 2.75" between the bottom inside surfaces of the shower drain elbow and the tank entry fitting. That is the distance from inside pipe bottom to inside pipe bottom. Do you think a p-trap will cause a drain problem due to its nature (drainage dropping below the entry into the tank) and a waterless might work better? I've wondered about the benefits between the two styles for the two issues of 1-minimal elevation and 2-slosh back. One the one hand, slosh back may be better controlled with water in a p-trap and o-ring at the drain stopper, due to the waterless trap flapper valve bouncing while under way. But if it allows seepage past it, the o-ring may catch that portion, and on the next turn/stop/acceleration the water will drain back down through the flapper. But on steep down hills will it push past both? Of course at those times most of the waste water weight will bypass a slosh back tendency just due to the position of the shower drain entry into the back portion of the tank.
Thanks for any thoughts you have on this.
