Grey Water Venting issues

[thubbard84]

I'm 99% sure I have a clogged vent line for my grey water holding tank. The outside vent looks like this one attached. My question is, is there any way to unscrew / pray off the chrome cover so that I can snake a wire down the rubber hose to clean it out? It's virtually impossible for me to remove the hose from the tank or the thru-hull vent fitting because of the tight space. I've tried using water and air but, neither one seemed to unclog the line.

 

[Slipin Away]

No, it is a solid piece that has holes on the side with small mesh screen that has probably clogged. If you can not remove the fitting try using a angled ice pick to pry screen out and maybe you could put a wire or plastic wire tie in then. Common problem on my boat as they rust out quickly, and blocks out the vent hole

 

[Rick486]

I just blast these fittings with the dock hose and that usually does it. They do seem to clog frequently though.

 

[Peggie Hall HeadMistress]

Those thru-hulls are designed for fuel vents...boat builders use the same kind on all vents 'cuz it costs 'em less to buy one type in bulk than to use the correct type for each type of tank. Waste holding tanks--and btw, I'm pretty sure your tank holds BLACK water (toilet waste), not gray water (galley, bath and shower water--need an open thru-hull that allows the vent line to be backflushed to keep it clear.

So pry or cut or do whatever it takes to turn the thru-hull into an open thru-hull...and
once you've done that you can put a hose nozzle up against and backflush whatever has clogged the line into the tank. To KEEP the vent line clear, backflush it every time you wash the boat and/or pump out. That'll take care of any insects that might try to set up housekeeping in it too.

 

[thubbard84]

Thanks everyone for your advice! Would anyone recommend me just drilling a large hole in the center of the chrome cover? Here in Seattle, we don't have a huge issue with bugs so I was thinking on leavening uncovered to help it vent more. I could plug it if you think it should be.

 

[Ralph Johnstone]

Would anyone recommend me just drilling a large hole in the center of the chrome cover?

Sounds like the best idea yet.

There's no need for protection from rogue waves hitting the side of your hull so the externals can be removed. I went as far as removing the internal loop from my vent line (factory installed) to ensure maximum ventilation. After all, it's only a holding tank.

 

[Peggie Hall HeadMistress]

I agree with Ralph...good plan. And I'd use drill bit--even a hole saw--big enough to cut the whole thing out instead of just drilling a hole in the middle of it. The only bugs you have to worry about are spiders and mud daubers, but backflushing takes care of any spiders and mud daubers are only a problem in the spring. They love to build their mud nests in open thru-hulls or anywhere else they can find to plug up. Those need a screwdriver blade or an ice pick before you can flush out the vent. I even had to scrape one out of the venturi tube on my gas grill one year!

And also get rid of any loop in the vent line. Those are needed to keep water out of fuel and water tanks , but it doesn't matter if a little water gets into a waste tank via the vent line.

 

[thubbard84]

Hey Peggie and Ralph,
I've attached some photos of what I did (it's really nice living only 5 min. from the boat.)
1) Protected the chrome and used a center punch to start drilling.
2) Created a small pilot hole with a small drill bit
3) Used a step-down drill bit and lots of oil and drilled a 7/8" hole (I might make this bigger.)
4) Used a water hose to clear out the blockage and pumped out. Worked like a charm!
Thanks for all the suggestions!

 

[Peggie Hall HeadMistress]

WTG I love it! However, the standard size for tank vent lines--and therefore the size all builders use--is 5/8" and all "vent" thru-hulls are also 5/8".

So unless a PO has upgraded the vent to much larger one (which would make it unlikely that he'd have used that type of thru-hull), I gotta ask how you managed to put a 7/8" diameter hole in a 5/8" vent fitting at all, much less still have a lot of room left to make it bigger.

 

[thubbard84]

Yikes! I meant 7/16".

 

[Peggie Hall HeadMistress]

That makes a lot more sense!

You said you might make the hole bigger...I suggest you drill the whole thing out. Opening it up will allow more air exchange with the gasses in the tank, which will help prevent odor...and the more open it is, the more pressure you can put behind water to backflush the line.

 

[Benny17441]

Did not think boats came fitted with gray water tanks. No restrictions against dumping gray water into the waterways.

 

[thubbard84]

Peggy is right, it's the black water holding tank.