My tank install is not ideal- am I setup to fail?

[Rich Stidger]

Peggie,I've got your book and have read it regarding the size and routing for vent hoses.This winter I am replacing the aluminum tank in my Hunter 40.5. It currently has one vent hose that is 3/4" and it rises more than 45 degrees and is 5-6 feet long. It is connected to the side of the tank about 1/3 of the way from one end.I want to add two new vents to my new tank and both would be at the top of the tank and centered port-starboard. One at the forward edge and one at the aft edge. The problem that I have is that I will still be stuck with a rise in excess of 45 degrees and lengths of 6+ feet. The clearance between the top of the tank and the bottom of the cabin sole is only about 1.75 inches. This means that I probably can't have enough clearance to get a fitting bigger than 3/4" and that fitting will have to be an elbow into the top of the tank with the hose coming off horzontally.All of these parmeters are not recommended in your book. Am I setting myself up for another stinky tank? My boat lives on a mooring so I am reluctant to install a powered vent system unless there is just no other way.I've attached a picture of my tank with locations of vents.Suggestions?

 

[Rich Stidger]

My goal is two-fold

First I want to replace an aluminum tank that is probably on it's last years BEFORE it fails. My boat is a 1997 and we have used it for 8 years. I have removed that tank and it shows no sign of leaking at seams but there was a drip from one of the inlet hoses. I couldn't tell if it was a leak or just the result of removing the hose and tank.I do have some odor in the area of the holding tank, but I have checked the hoses per your method of hot damp cloths and have not observed a beyond-a-doubt hose failure. However, failure or not, the hoses are going to be replaced also. I also understand that I may have some trapped stagnant water somewhere and I will try to see if I can find any, but that is very difficult. I believe that there are many spots that cannot be seen or reached within the hull gridwork. I may never find anything.The primary odor I am trying to eliminate is out the vent. I have used Odorlos for 5+ years, and the tank is pumped every week. My boat is on a mooring and the tank is pumped by the town during the week when I am home. Thus I cannot immediately add more Odorlos until I arrive several days later. Also, flushing with water at each pumpout is also impossible.Please note that I am proposing to replace the SINGLE 3/4" vent with TWO 3/4" vents, and relocate them from the side-center of the tank to each end on the top of the tank. My hope is that I can create an opportunity for natural cross-ventilation.Hope this clarifies.

 

[Don]

Rich

I just went thru this on our 40.5 a few months ago - having to pull the tank which I thought was leaking. Long story short - it wasn't the tank but a hole in the vent line allowing odor to escape inside the boat. Just in case you are contemplating using the same vent hose, it's probably not a good idea if mine is any indication. Don

 

[Rich Stidger]

Good input Don

I plan to replace all of the hoses. The only exception may be the forward head hose depending upon how difficult it is to replace.Did you replace your forward head hose and if so how hard was it to snake a new one in place?

 

[Steve Dion]

Let's get some feedback from Rick Dinon.

Rich:We have had the replacment hoses on our Hunter 31 for about 10-12 years and there have been no major problems with odor. We have been using Odorlos for several years. The only time we have ANY problems is when I let the tank level get a little high. Our vent is still the one that came with the original tank (1985). I think that it is 3/4 but I am not sure. Rick Dinon has just replaced his tank on his 40.5. He should have some input on a replacement tank.

 

[Rick D]

No Tank Yet

My tank is still being made. I am going with a 1" vent in the stock location. That, however, will not get the cross flow that Rich wants. Rich is a much better engineer than I, so being a coast apart from the fabricating shop, I decided to minimize the alterations. Rick D.

 

[Steve Dion]

Rick, Where did you order it from?

Rick D:Where did you order your tank from?

 

[Rick D]

Tank Sourced from Triple-M Plastics

Steve: here is the link to them. Shipping was an issue until I got it at a reasonable rate by shipping to a business. RD

 

[Don]

Rich - fwd head hose

RichI didn't attempt the fwd hose as we use that head so infrequently, I assume (read hope) it wasn't worth the effort. Seemed to me that I would have had to remove the sole board under the port settee to get good access which as you know means removing the two compressors and water heater and it seemed like a real bear to snake a new hose through that maze with the floor in place.The biggest thing I learned from this was to trash all those corrugated hoses as the vent seemed to be cracked throughout its length inside the folds making visual inspection impossible.Don

 

[Rich Stidger]

Peggie, more details and answers

Yes, the tank is located under the cabin sole. I am stuck with that location- there is just no other spot to install a tank. This location requires that the vent run mostly vertical in order to get above the heeling point. You said that I can't get any cross ventilation with hoses that run near vertical and are on the same side of the boat. Unfortunately, I cannot change that configuraton. There is not way I can get one vent to an opposite side and even if I could it would be 10 feet long and still have to rise vertically.Regarding flushing the tank upon arrival- I am 15 miles from the 3 mile limit so I cannot conveniently go there to flush the tank. My marina has a pumpout boat that must be scheduled in advance and no dock pumpout is available, so flushing with sea or fresh water each week is just not possible.I may be able to leave a gallon of water with Odorlos in it and leave a note asking the pumpout person to dump it in the tank when he is done.I cannot flush the tank in the manner you describe via the deck fitting because the macerator input is tee'd off the deck pumpout so that if the cap if off the deck (to add water) the macerator just pulls air from the deck. I can only fill, replace the cap, and then pump.Whenever I take on fresh water, I do flush the vent. Also if I over-flow the vent (not very often) I flush it with my wash-down hose as soon as I am pumped out.What is a salt water tank flush? It sounds like a permanently plumbed-in connection to my deck wash down that I can simply open a valve to let seawater into the tank.If I cannot be succesful in obtaining a passive cross-ventilation system, maybe my only alternative is to put in a forced air system.