New waste tank ventilation

[mregan]

I'm going to be replacing my waste tank with a similiar tank from Ronco.  I'm remembering from Peggy Halls book mention of adding a second vent line to create a cross ventilation in the tank to stop odors from the waste breakdown.  I'd rather not run another vent through the boat but was thinking of maybe installing a fish tank air pump.  I was thinking of putting two openings in the top of the tank. One for the vent, the other for a 3/8" fresh air line from the pump.  My thought is the pump would pressurize the tank and force the air out the vent creating ventilation in the tank.  Thoughts?

[Roland Gendreau]

I have experimented with a similar setup this season.   I added a 12 volt aquarium pump piped into the top of the holding tank, with the existing vent in place (thru the stanchion). 
When the pump was first turned on, there was a pretty good blast of odor from the vent. I left it running while at the mooring,  for a few days. When I returned a few days later, all odor was gone. Flushing the head seemed to produce no odor at all.   

The only drawbacks are the sound the aquarium pump makes, and the small power draw.   What I would like to do is set the pump up on a timer that would run it a few hours per day, and see how much ventilation is really needed to keep the tank odor free.   

I purchased the pump on amazon.com. I can provide specifics if you need it.

[mregan]

Yes please.  I was thinking of getting a 115v pump and have it run all week at the dock while we are away.  Although if we are on shore power, the 12v would work also.

[Roc]

I seem to remember Peggie not being too fond of putting aquarium pumps to drive air into the holding tank.  Here is my set-up.  The hose is routed along the port side, through those cubby storage holes behind the cushion.  Runs forward into the port v-berth cabinet and out to a through hull near the sheer stripe.  I kept the orignal vent line that leads to the stanchion.  Helps with cross ventilation.  When I did this, I actually called Peggie and spoke to her about this.  She felt it sounded good.

[Roland Gendreau]

 
The 12 volt aquarium pump  I purchased is here:

http://www.amazon.com/gp/product/B002QFXUDG/ref=pe_140030_120540520_em_1p_0_ti

I did a quick search on 12 volt timers and there are a number of them available on Amazon.

[Noah]

Roc --How does your vent through the side of hull at the shear stripe working? What size fitting/hose did you use?  Did it solve the odor issue? Any downside after a year in operation?

[mregan]

Thanks Roland. 

Roc.  Did the second vent do the trick?

[Ken Juul]

I have also changed the vent line placement. Same size hose, vent between the boot stripe and rub rail.  Odor reduced 30-40%.  The original vent is still in place.  One of these days I'll plumb it into the tank for some cross ventilation.  Electronics, exhaust riser, battery charger, etc all failed last year.  Need to ration the boat bucks.  Regular pump outs seem to help as much as anything.

[Roc]

In my discussion with Peggie, she suggested the largest hose that will possibly fit.  I'm guessing I used a hose about 1" to 1-1/4" diameter.  I drilled a hole into the inspection cap as you can see (did that because I felt if anything went wrong, all I needed to do is buy a new inspection cap  ).....

The large vent near the sheer stripe allows air to freely enter the tank.  Kind of like an air-dam on the hood of your car.  Peggie suggested a gradual climb from the tank to the exit thru-hull.  That's why I didn't just run the hose vertically from the inspection cap fitting directly up.  Instead, the hose runs forward, in a gradual upward slope to the area right behine the v-berth cabinet.  As close to the rub rail as possible so heeling won't allow water to suck in, and forward enough so the air gets pushed in.

I did this as soon as I bought the boat new in 2000.  So there have been no issues all these years.  Peggie suggested I keep the original vent line, since that would only help with ventilation.  Absolutely no head odors.  I use CP to clean the toilet.  I put Odorloss at the end of every stay on the boat.  I also flush the toilet using only fresh water, which I plumbed a "T" in the head sink drain.  I put fresh water in the sink (with the seacock closed), and pump the head as normal (wet bowl/dry bowl).  I've read where people use vent line filters among other things to combat odors. That's a bad idea since you are plugging any possible way for air to freely enter the tank.  Read Peggie's methods and it's really a simple set up to eliminate head odors.

[mregan]

I think our other big issue is we use sea water to flush the bowl.  I keep telling the family to pour cups of fresh water from the head sink into the bowl but nobody listens. 
Also, it doesn't help that we pumped out Saturday, 10 minutes later I'm at the dock putting the sail cover on, and my 10 year old decides to do #2 on the boat rather than the marina.  I can't win.

Added 9/25/'14 - Stu:  Head Pumps 101  Why just pouring water into the bowl is NOT a good idea http://c34.org/bbs/index.php/topic,5865.msg40604.html#msg40604

[Roc]

You have to get the family to use the land facilities whenever possible.  Actually, the holding tank is so small, you can't use it all the time, when other facilities are readily available.  About pouring the fresh water into the bowl... that won't do anything about the sea water smell.  You have to flush with fresh water by plumbing the intake using fresh water (with a "T" from the sink drain).  Reason is the water needs to go "THROUGH" the inside of the bowl and out the rim holes.  If you don't do that, you are just keeping stagnant sea water INSIDE the bowl, which is causing the smell.  You need to keep fresh water moving INSIDE the bowl, out the rim holes, and down to the holding tank.

[Ted Pounds]

I think our other big issue is we use sea water to flush the bowl.  I keep telling the family to pour cups of fresh water from the head sink into the bowl but nobody listens. 
Also, it doesn't help that we pumped out Saturday, 10 minutes later I'm at the dock putting the sail cover on, and my 10 year old decides to do #2 on the boat rather than the marina.  I can't win.

It does get better.    And, trust me, 15 years from now you'll be looking back fondly on these days, and maybe even yearning for them to return...   

[mregan]

That's what my wife keeps saying.  I keep counting down the days until they are off to college.

[Ted Pounds]

When our first went off to college that's when we had to sell "Molly Rose" - to pay for Molly's college...