Odor outside after flushing head

[Babacoc]

On our RT 31, we’ve noticed a sewage smell outside the boat when we flush the head. The overboard shut-off valve is closed. We regularly put deodorizer in the holding tank, but even if we didn’t, why would we smell sewage outside the boat? Isn’t the waste going directly into the holding tank?

Second question — what’s the best way to flush out the holding tank?

 

[dbsea]

there's a holding tank vent, which is where the odor is most likely coming from.

You'll want to do a few things:

Change your holding tank vent filter:

https://www.amazon.com/gp/product/B00E5 ... UTF8&psc=1

pump out your tank and then fill it with water from a hose (through the pump out port outside) and add this to the toilet and flush (do this annually):

https://www.amazon.com/gp/product/B0741 ... UTF8&psc=1

leave it overnight and pump it out again.

thirdly, after each following pump out, add one of these to the tank via the toilet:

https://www.amazon.com/gp/product/B0015 ... UTF8&psc=1

I always make a habit of rinsing the tank after each pump out. takes a bit more time but worth the effort...

 

[watson1987]

Does the R31 have a vent filter? If so, where is it? I've never changed mine, and do sometimes get a smell despite flushing the tank, using deodorizer tabs, and nuking it with a gallon of vinegar after some pump outs

 

[Babacoc]

Thanks for this, Halcyon. How often do you change the holding tank vent filter?

 

[Robvic]

Our R31 did not have a holding tank filter. I installed one behind the fridge just below the vent (and more importantly high above the tank). I changed it annually.
Rob

 

[watson1987]

Our R31 did not have a holding tank filter. I installed one behind the fridge just below the vent (and more importantly high above the tank). I changed it annually.
Rob

Oooff, did you have to remove the fridge annually in order to complete the filter change?

 

[PNWTX]

On our RT 31, we’ve noticed a sewage smell outside the boat when we flush the head. The overboard shut-off valve is closed. We regularly put deodorizer in the holding tank, but even if we didn’t, why would we smell sewage outside the boat? Isn’t the waste going directly into the holding tank?

Second question — what’s the best way to flush out the holding tank?

Yes, the odor is coming from the vent/displacement inside the holding tank. We had terrible odor issues. I tried everything. Nothing seemed to work until we switched from raw/salt water flush to fresh water. That made all the difference, and have not smelled anything ever since.

 

[fishheadbarandgrill]

Add this book to your Amazon shopping list. https://www.amazon.com/Get-Boat-Odors-P ... 1892399156

The author is Peggy Hall and she's known as the "Headmistress". You'll learn why your head stinks, and why head treatments don't work as well as they should. Marine holding tanks typically, and RTs are no different, don't have large enough vents to allow for aerobic decomposition of the bacteria. As a result, anaerobic bacteria take over producing methane gas which sits on top of the tank until the contents of the tank force the methane out the vent line. Thus, it stinks when you flush.

That's why some owners have installed filters in their vent lines. Install the filters too low in the vent line and you risk the chance of contaminating the filter with liquid gold.

We've chosen not to install a vent and simply treat the tank with https://www.amazon.com/Raritan-Kills-Bi ... C89&sr=1-1

It's worked the best so far in enhancing aerobic bacteria growth, but, eventually, the anaerobic bacteria win the battle and we get a smelly flush before pumping out.

 

[dbsea]

Thanks for this, Halcyon. How often do you change the holding tank vent filter?

I think it’s an annual maintenance item… mine is in a very hard to get to location behind a rat fur panel way forward in the quarter berth in my CB30.

 

[SJI Sailor]

Same as PNWTX -- freshwater head conversion has meant far, far less odor. We did that conversion instead of a vent and have been very happy.

Zaal or Odorlos (or sodium percarbonate) help, too. Also, after pump out, if no one is waiting, fill it half way or so with the black water hose (where available) and do an extra pump out cycle or two.

 

[Cutwater28GG]

I like the ZaaL NoFlex digestor product.

pump out often and flush with fresh water helps a lot.