Waste tank plumbing idea...

[yarrumretep]

Greetings forum, My holding tank is fitted with a hose-barb outlet on the bottom of the tank for evacuation. My thinking is that as the tank fills, whatever hose that is connected to that barb will fill accordingly with the level of the waste in the tank. Doesn't this put extra load on the impermeability of said hose for that length? What if I were to replace the hose-barb with a PVC elbow and plumb a section of hard PVC for the "rise" of the route until it's over the level of the tank - then switch to high quality hose for the Y-valve, o'board pump and deck pump-out lengths (which would presumably be mostly empty except during actual pumpout sessions).

Am I thinking about this correctly? Would this help prevent odor issues over time?

Best,

pete

 

[Tally Ho]

Yes, you are right that the the low end of the hose will be filled with waste, and hasten the demise (permeability) of the hose.

A hard pipe can solve that.

Greg

 

[dlochner]

Using a high quality hose, like Raritan Saniflex will also reduce holding tank odor as will using a good quality vent hose and appropriate holding tank treatments.

The issue with hard plumbing on a sailboat is the constant flexing of the boat. Unlike a home a boat constantly twists and turns and moves. This can be damaging to hard plumbing. So yes, hard PVC can be used but it should be installed to accommodate the boat's movement.

Another method is to move the outlet to the top of the tank and use a dip tube to reach the bottom. This keeps effluent out of the soft hoses and reduces odor. It does require clearance at the top of the tank for the fittings.

 

[Peggie Hall HeadMistress]

My holding tank is fitted with a hose-barb outlet on the bottom of the tank for evacuation.

Is it actually IN the bottom of the tank, or is it AT the bottom of a vertical tank wall?
if it's at the bottom of a vertical tank wall, a piece of schedule 80 pvc long enough to reach the top of the tank is a good solution. You'll use a 90 degree thread- smooth fitting coming out of the tank...the tricky part is sizing the "parts. That fitting (which you'll prob'ly find in the plumbing dept of a big box or large hardware store) needs to accept a pipe that that has an OD (outer diameter) the same size as your pumpout line--which is certain to be nominal 1.5" so you can just slip the pumpout hose onto it, secured with two hose clamps, without the need for a hose fitting. Warming hoses a bit makes them much easier to slip on fittings or hard pipe or remove old hoses.
You'll use PVC cement or "glue" of your choice to secure the pipe to the 90, but nowhere else.

As others have suggested, I recommend you use Raritan SaniFlex hose--which is top rated--throughout your system. It not only has a 10 yr warranty against odor permeation, but is so flexible that it can be bent almost as tight as a hairpin without kinking which makes most hosereplacement jobs a LOT easier. Defender has it for $10-11/ft and sell it by the foot, so you only have to buy the amount you need. Raritan Sani / Flex Sanitation Hose at Defender

--Peggie

 

[yarrumretep]

Hi Peggie - the barb is coming out of the bottom of the tank not the side at the bottom. I'd need two 90s to accomplish what I'm considering. Or I just get the raritan hose and call it a day!

-pete

 

[Peggie Hall HeadMistress]

First... I just realized you only joined our merry band yesterday...welcome aboard!

That's only done in tanks intended to drain via gravity without the need for an overboard discharge pump. For that to work the tank must be entirely above waterline...the line from the tank goes directly to a below-waterline thru-hull. Its seacock is kept closed except to dump the tank (only where legal, of course). Hard pipe isn't recommended for that line, so your only protection from odor permeated hose is exceptionally odor resistant hose.

But you also need to be able to pump out the tank...and while doing that, rinse out the sludge that builds up in the overboard discharge line, which requires opening the seacock--only AFTER you've pumped out and rinsed out the tank. Hopefully you have at least 5" clearance above the tank, 'cuz that will allow you to install a new discharge fitting in the top of the tank--which, thanks to a li'l gizmo called the Uniseal UNISEAL, is actually pretty easy to do if you're at all handy with a hole saw--and schedule 80 PVC to make a "diptube" (detailed instructions to follow if you want/need them).

You're welcome to contact me directly if you want to discuss in more detail than is practical in a discussion forum.

--Peggie

 

[yarrumretep]

Hi Peggie - thanks for the welcome - and the really great responses throughout this forum!

More grist for the mill: The tank itself is a plywood / fiberglass tank made by a well established boat building outfit - and partially installed in my (new to me) boat. The fitting is a bronze (is that legit in waste water situations?) 90-deg 1 1/2" barb fitting screwed into the bottom of the tank. The input is near the top of the tank - also bronze 90 deg in the aft side of the tank. There is a "cleanout" / sensor cap in the top side and a 3/4" vent 90-deg bronze barb forward on the top of the tank. I do not believe the tank is totally above the water line - but will confirm that next time I'm on the boat.

My plan had been to plumb the bottom barb to a y-valve with one branch going to a deck-plate and the other to a diaphragm pump, siphon-break well above water line and then to the discharge seacock. My concern was that the waste water would sit for long periods in that section from the bottom of the tank to the y-valve (which I would be sure is higher than the top of the tank). So my thought had been to make a hard section for the rise from the bottom to above the top of the tank, then plumb the rest as described.

 

[MikeHoncho]

I used pvc to eliminate all flexible hose other than short sections to joint dis-like inner sizes and it worked great. Design into your system a way to take it apart without having to cut the pvc while isolating the tank as you will always have fluids left in the tank following pumping out. I used pvc ball valves and compression couplings.