Dave Pete wrote:
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.
Dave , I posted your picture to use as reference , I'm not very good at computer wizardry as you can tell .
My thought on the shower drain was to come out of the shower fitting with a straight tail piece and connect a fernco 1-1/2" trap . At the tank end come out with a stub pipe and connect a fernco ell . Then make up a pipe with an ell on one end to connect to the trap ( making it a P shape trap ). That would make all the connections with fernco's , no nuts and washers , and easy to disassemble . You mention using 1-1/4" drain because of low water usage and this could very well be , but since the shower drain is 1-1/2 and the tank is 1-1/2 , why not keep it all one size . I don't think it will affect the sloshing one way or the other .
If you have one vent path for the grey tank that should be sufficient , no need for multiples .
The sloshing problem is only when underway . When set up level and stationary all the sloping of pipes and elevations of drains and tanks makes sense . Once moving over uneven roads , up and down and side to side , all of that is out the window . Since I don't have my shower drain connected to my grey tank as yet , it has not been a problem . More and more I have been thinking of using a plumbers test plug in the shower drain when traveling , they come in a number of sizes . have not tried the waterless type trap so don't know how good it will work , especially under mobile conditions . You could be the first in your neighborhood .:D My general philosophy is anything with moving parts is more prone to failure .
Hope this helped more than hindered .
