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Drain/holding tank for small shower

Aug 3, 2021
Rawson 30 Juneau
Hi all,
I am eager to redo my "shower" in a more proper manner. Currently, the water drains into the bilge through a slatted floor (or "sole" i believe in sailors terminology, make of Trex decking. I lifted up a piece for the pictures). This rests on tabs against the hull, and side bulkheads.
The problem is how to design the space to create a shower pan with a single drain that leads into a holding tank. Does anyone have any ideas? Pictures of a shower with a toilet in such a small space?
The boat is a 1960s Rawson 30'. There is a manual Jabsco toilet that pumps through the bulkhead on the left into a Lectrasan tank. There is room in that space for a holding tank, but I don't know how to build a shower pan that collects the shower drain water and plumbs it "uphill" in such a manner. The space beneath the current slatted floor is very small, probably too small to have the holding tank under it.
What I've considered is to raise the floor level enough to put a holding tank underneath, though I may end up crouched and I don't know if the toilet would fit anymore.
The bare fiberglass hull is visible under the lifted floor panel. Above that, the hull is insulated with some foam and finished with FRP (fiberglass reinforced panels) typically used in home construction. The toilet sits on a wooden box merely for usability comfort.


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Jan 1, 2006
Slickcraft 26 Greenport, NY
The shower sump doesn't have to be very big. The one on my H356 probably held less than a quart - maybe a lot less. The key is to have a sump pump which empties the sump as it fills. You can probably find an after market sump and pump but making a version won't be that hard.
You need a plastic container (Laundry soap container) which you can modify to fit almost any space. You can place a small pump in it with the appropriate electric and discharge connections. You don't need a 1200 gallon per hour pump. I think self priming would be best. Then you have to clean it regularly since soap, hair and discarded skin cells make a smelly mess if allowed to co-habitate.
May 17, 2004
Beneteau Oceanis 37 LE Havre de Grace
+1 for the sump pump. It should be possible to do that using just enough space for a sub-floor drain tube and a very slight recess for a drain hole in the lowest section of the pan. There are shower sump pumps that are pretty resistant to clogging, and a separate screen filter can be added too if necessary, all above and away from the shower pan.

Is there any reason you want to use a holding tank and not just pumping the gray water overboard? It’ll save space to not need a tank, even if you can put the tank elsewhere.
Jan 7, 2011
Oday 322 East Chicago, IN
In addition to the shower sump idea, another alternative is a shower pan, with a drain connected to a pump directly ( no sump per se). My O’Day 322 is set up that way…the shower pan has a drain and hose connected to a pump in the vanity, that pumps overboard. I think this method was used because I have no room under the shower pan…just enough for an elbow under the drain. The own side is I have but turn the pump on and pretty much keep it on while using the shower. There is an on/off switch in the head, so easy to turn the pump on and off. My set up uses a diaphragm pump, which is pretty loud.

It seems like either way, you need to fabricate some sort of shower pan, so you can capture the water into a sump box or the hose connected to a pump...unless you can just close off your bilge under the shower so the water stays there, and you can fit a pump in there to evacuate it reasonably well.

Dec 2, 1997
- - LIttle Rock
There are two places you DON'T want shower water to go--the bilge and your toilet waste holding tank...in fact, it's actually illegal to put it in the holding tank and t he bacteria, soap scum etc in shower water will give you a very stinky bilge. So the suggestions to install a shower sump with sump pump are good ones. You may just have to plumb it to put the sump somewhere near the shower drain instead of directly below it.

Aug 3, 2021
Rawson 30 Juneau
Wow I appreciate the replies! Controlling the bilge stink is my motivation for this project.
I do not "need" a holding tank. I thought it would be on the less legal side to directly pump my shower water overboard. Of course that's what is happening now by draining into the bilge. Maybe it's not clear in the picture, there is currently a small bilge pump in that space below the shower floor that pumps into the main bilge compartment. I could reroute this hose directly overboard, but that would still leave a difficult to clean space underneath that would get stinky. Currently I wash this area (and the main bilge) about once a week, because of the stink. But of course these are difficult to clean areas, and the porous cement never really gets entirely clean.

How would you go about fabricating a shower pan for this space? I'm imagining replacing the slatted floor with epoxied wood or some plastic/synthetic material into which I've drilled a drain in a low spot, which is plumbed directly overboard, via an inline pump. I have an unused seacock next to the toilet, but to use this would mean the drain hose would have to come back up through the showerpan floor to get overboard, so a sort of U-bend to reach the sea cock next to the toilet, and an extra penetration through the showerpan. Or else take a much longer route through the bilge and T junction in to the overboard bilge hose?
And how to attach this pan in place? Epoxy to the tabbed sides so it cannot be removed?
Currently the pump switch for this compartment is in the head so rewiring is very easy.
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Aug 3, 2021
Rawson 30 Juneau
Wow, very cool what he did. I don't see where he's going to run the drain hose from under the showerpan, or attach a pump, but regardless, I think his skill/time/effort/space to work far exceeds what I am capable of. I'm hoping to use some plastic sheet (like a solid surface countertop?) as the showerpan so I don't have to lay so many layers of fiberglass ontop of plywood. Though I won't get such a nice fit, I do like the idea of using several pieces puzzled together to create a nice slope angle.
Thanks all for your support, great info so far.