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Old 08-15-2019, 05:34 PM   #21
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Originally Posted by Todd S View Post
The issue occurred after the last pump out. I believe that the pump out vacuum did it. I assume it flexes under vacuum and became fatigued more and more with each successive pump out. Certainly the tank became concave, over time, on the large top. Ironically, the bottom was flat.

And yes, I will make floor over the tank easily removable so that the tank and all the fittings are easily accessible.
When you order the new tank from Ronco Plastics, make sure to order a thicker plastic holding tank. Also two 3/4" to 1" tank vents.

Plastic tanks come is several wall thicknesses. Boat manufacturers sometimes install the thinner wall tank for cost savings. The thin walled tanks tend to expand and contract with pumping out or with Vacu Flush. Eventually cracking or bursting.

Two larger vents will prevent vent clogging and allow higher air flow during pump out.

Thicker tank walls will prevent flexing and cracking.
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Old 08-15-2019, 09:22 PM   #22
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Good point about vent being plugged. Chances are that was the issue. Iím replacing all hoses as well as the vent line. I obviously will be more careful with that going forward. Thanks

I'd bet money that a blocked tank vent is what cracked your tank. All tank vents have two main functions: to provide an escape for air displaced by incoming contents and provide a source of air to replace contents as they're pulled out. When air displaced by incoming waste cannot escape out the vent the tank becomes pressurized, creating increasing back pressure that prevents the toilet from flushing.

Without a source of air to replace contents as they're being sucked out of the tank, the pump will pull a vacuum that'll prevent it from pulling out more than a gallon or two. A particularly strong pumpout can even implode a tank.

Just replacing the vent line may not solve the problem 'cuz 99% of vent line blockages aren't in the vent LINE...the two most common locations for a vent blockage are the vent thru-hull and the other end of the vent line--that end of the hose and the vent fitting on the tank (since you're replacing the tank AND the vent line, that won't apply to you). So before you replace the vent line, clean out the vent thru-hull...use a screwdriver blade, ice pick--whatever works. Or better yet, replace the "vent" thru-hull--which is actually designed to keep sea water out of fuel and water tanks, which is hardly necessary for waste tanks--but boat builders save money by using the same thru-hull on all tank vents--with an open bulkhead or "mushroom" thru-hull. That accomplishes two things: allows more air exchange with gasses in the tank--essential to preventing odor out the vent--and allows you to put a hose nozzle against it to backflush the vent from thru-hull to tank, preventing vent blockages.



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Old 08-16-2019, 06:53 AM   #23
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Thanks for all the great responses & the pics sent. Ultimately, the floor had to be cut out to remove the tank. Currently in process with installation of new tank.
Attached 3 pics.
Is there a sticker on the original tank showing the maker's name and sidewall thickness and so forth?


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When you order the new tank from Ronco Plastics, make sure to order a thicker plastic holding tank. Also two 3/4" to 1" tank vents.

Plastic tanks come is several wall thicknesses. Boat manufacturers sometimes install the thinner wall tank for cost savings.

Thicker tank walls will prevent flexing and cracking.
Adding to that, Ronco makes two different thicknesses for many (all?) of their tanks, one usually installed in RVs and the other more "marine."

The Ronco marine-version tank we installed is indeed thicker than our OEM tank was.

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Old 08-16-2019, 09:44 AM   #24
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Ronco makes two different thicknesses for many (all?) of their tanks, one usually installed in RVs and the other more "marine.


Ronco Plastics does NOT make the same tanks with different wall thickness for the marine and RV market. They have separate marine tanks (shown as "boat" tanks on their home page now for those not smart enough know what "marine" means) and RV Tanks catalog sections and use different mold numbers for each type. This is the direct link to their marine tank catalog Ronco Plastics marine Tanks and is the only link I ever provide to boat owners or post to boating sites because the specs for marine and RV tanks are not the same. All their marine tanks have a minimum 3/8" wall thickness--typically 50% thicker than most other mfrs "standard" tanks--and reinforced corners...wall thickness begins gradually increasing as needed above 40 gal. to support the weight of the contents (8.333 lbs/gal).


Al that said, it doesn't matter how thick the tank walls are...a blocked tank vent can even split a stainless steel tank.



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Old 08-16-2019, 10:18 AM   #25
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Don't remember how I got there from here, but when we were searching on their website I think we started with gallons and went from there. I think we didn't start with either marine or RV, mostly being focused on dimensions. I do (think I) remember it took me a few minutes to figure out that one of the first search returns wasn't the heavier "marine" version.

Now that you've mentioned it, I just went to look and don't see our tank size in the RV-related tanks at all, now... but I probably have their mold number that I saw back then on the home computer somewhere...

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Old 08-16-2019, 10:54 AM   #26
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When you go to Roncos home page, there is a tab for "Boat Tanks"

When you place a Ronco tank order, make sure you draw a diagram with accurate dimensions. They manufacturer the tanks with the fittings exactly to your dimensions.

There are no returns unless it's their mistake.

You might get a better price on Ronco tanks by ordering through a marine sanitation dealer or some other business. There is a hefty mark up on the tanks. I usually discount the tanks ordered through my business.

Buyer pays the shipping fee.
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Old 04-18-2020, 09:57 PM   #27
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Quote:
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Good point about vent being plugged. Chances are that was the issue. Iím replacing all hoses as well as the vent line. I obviously will be more careful with that going forward. Thanks

How did you access the hoses under the shower that pass through the stringer to connect to the tank? Or, did you run them via a new route such as through the washer/dryer space under the stairs? Iím ready to replace my hoses, but I cant see how to get to them where they disappear after coming out of the tank, short of perhaps cutting an access hole in that wall, assuming I can clear the shower.
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Old 04-19-2020, 12:38 PM   #28
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Iím sure how my comments fit in, but here it is!

Itís not necessary to remove the hole floor, only about 10 inches at the stern side. Then move the thank backwards and lift the front end up.
Replace the missing floor with a cover of aluminium plate designed like a stair, to protect the pump.
It will also make it easier to maintain the sensor.


The final solution for the odour problem in MS 400.

I have comments this before, but here is it again.

On ours 400, 2005 the through-hull fitting vent was completely blocket by growings and also by carbonfilter. Furthermore, the existing vent line has a bad design, it's to long and to small with severall watertraps.
The thru-hull vent gear was not a good choice Mainship did. (unfortunately make many boatbuilders the same choice). They're made for fuel vent in order to avoid water in to the tank. The holdingtank-vent shouldn't be blocked. It should be easy to spray in water with a hose, once in a while.
It's very difficult to change the existing thru-hull vent so I drilled a 12 mm hole from the outside in the middle of the water trap in the existing one.
And removed my carbon filter wich had became wet and blocked the air vent. There shouldn't be any filter in the vent line, according to Peggie Hall. I agee with that.

I changed to a bigger vent hose, 1 inch, and made a new pipe fitting into the rear end of the tank. It's qiute easy job to do.
The new vent hose became lot shorter and was mounted upwards with no water traps, witch is essential.
I pulled a second bigger vent hose in to the existing vent pipe in the frontend of the holdingtank to a new thru-hull vent in the front of the boat just under the anchore. It was quite easy to do with only one hole to drill in the removeable plate under the anchor.
There is now a new thru-hull vent in the bow and the existing one on the starboard side, wich together makes a good air flow, like in Peggie Hall's describe in hers book.

Lack of air in to your holdingtank makes the odor. Check the air vent by blowing.

It certainly solved ours odor problems, since some years back.
A good idea is to make the thru-hull vent fitting in the bow able to fit a hose in order to rinse the holdingtank with freshwater from one end to the other through the tank.

Good luck,
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Old 04-19-2020, 12:50 PM   #29
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NOT sure !
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Old 04-19-2020, 03:35 PM   #30
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I agree with the comments as to the vent hose being highly inferior. I was shocked to see that today, and it’s mounted to come out the side of the tank about an inch and a half from the top which means when the tank is full, it runs into the vent line, then the vent hose runs down before it turns back up again. Mainship really missed the mark there. My Hatteras had a 1.5” vent hose and I expected to find that on the Mainship, but no.

As for the replacement of my hoses, I have decided to run new routes, and most of it will be PVC pipe, rather than hose. I’ll use hose at transition points such as joining the PVC to the tank, joining PVC to the vacuum generator, and joining PVC to the hose that attaches to the deck plate at the last point where I have access. That worked very well on the last boat I plumbed that had four heads with the longest run being about 50 feet.

The 1.5” pipe fits perfectly along a little ledge on the side of the washer/dryer without interfering with future removal of that unit for service, and I can stack one on top of the other. I’ll leave the old hoses in place, unless I can yank them out somehow, and spray expanding foam insulation in them to seal them off to keep the coodies inside. That vent is going to get moved to the top of the tank with a 90-degree fitting and I’ll plug the old hole. Yeah, it will be bigger, too.
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Old 04-20-2020, 01:49 PM   #31
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Quote:
Originally Posted by Mermaid View Post
I agree with the comments as to the vent hose being highly inferior. I was shocked to see that today, and itís mounted to come out the side of the tank about an inch and a half from the top which means when the tank is full, it runs into the vent line, then the vent hose runs down before it turns back up again. Mainship really missed the mark there. My Hatteras had a 1.5Ē vent hose and I expected to find that on the Mainship, but no.

As for the replacement of my hoses, I have decided to run new routes, and most of it will be PVC pipe, rather than hose. Iíll use hose at transition points such as joining the PVC to the tank, joining PVC to the vacuum generator, and joining PVC to the hose that attaches to the deck plate at the last point where I have access. That worked very well on the last boat I plumbed that had four heads with the longest run being about 50 feet.

The 1.5Ē pipe fits perfectly along a little ledge on the side of the washer/dryer without interfering with future removal of that unit for service, and I can stack one on top of the other. Iíll leave the old hoses in place, unless I can yank them out somehow, and spray expanding foam insulation in them to seal them off to keep the coodies inside. That vent is going to get moved to the top of the tank with a 90-degree fitting and Iíll plug the old hole. Yeah, it will be bigger, too.
Take some photos along the way if you can, I'd like to see it visually!
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Old 09-10-2020, 04:06 PM   #32
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Re-plumbing options?

So with all this conversation I just checked mine . . .the tank has an expanded top, and when I removed the hose from the tank fitting, a gasp of air occurred. The hose is plugged, and I'm surprised there is no access to the vent; I would like to have replaced it with a mushroom. So now I have to find a good place for a new and larger vent.
I'll keep an eye on this thread to see what others are doing.
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Old 09-10-2020, 05:25 PM   #33
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You're lucky you didn't get a spew!

It's possible there's a blockage in the vent line, but I'd bet $1 that it's in the vent thru-hull...to which you do have access 'cuz it's on the outside of the hull.

The two most common locations for a vent blockage are the vent thru-hull and the other end of the vent line--that end of the hose and the vent fitting on the tank. You eliminated the vent fitting on the tank when you pulled the vent line off. Now that it's off, check that end of the vent line and scrape out whatever you find. Next clean out the thru-hull...use a screwdriver blade, ice pick--whatever works. If there's a screen in it, knock it out...screens cause more problems than they prevent. You won't get any "reaction" after you clean out the thru-hull 'cuz the vent line is no longer connected to the tank.

"Upgrading" to a larger vent requires more than just replacing the thru-hull with a larger one...the vent line must be larger too which will require installing a larger vent fitting on the tank--which is actually a pretty easy job for anyone who's handy with a hole saw, thanks to a li'l doodad called a Uniseal UNISEAL. When selecting a new location for the thru-hull, find one that'll let the vent line be short--ideally no longer than about 5', STRAIGHT and as close to horizontal as possible. If you'd like some one-on-one help in choosing a good location, you're welcome to give me a shout via PM.

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Old 09-10-2020, 10:36 PM   #34
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So I tried to run water from the outside into the boat's thru hull and not a drop came through. So I can clean the guts out of the thru hull and re-connect the small hose to the upper side of the tank, but I still need to introduce a new and larger vent. I've read a lot of what Peggie has written and am very appreciative of her guidance, and I will get the 1" size Uniseal installed. But that still leaves running a new hose to a new thru hull, which is something I may leave for the professionals. I'm just not sure if I could drill a nice sized hole into my boat's side!
But I'll keep watching and reading.
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Old 09-10-2020, 11:10 PM   #35
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A very easy trick to locate where to drill a hole in the hull or most anything is to get 2 strong rare earth magnets and tape one to the inside of the hull where you think the hole should go. Then go outside the boat and hold the second magnet around the area you think the hole will be, the magnet will find the one taped inside and stick to the hull. If it is good outside then mark the hull and drill away. You will know that there isn’t anything in the way on the inside. If you don’t like the location on the outside then move the inside magnet to another location and try it again. I have used this for years and it takes all the guess work out of where to drill, no measuring just let the magnets do the work. That way anybody can drill a through hull with confidence. Good luck and go for it. Just remember to drill from the outside into the hull and not from the inside out so you will get a clean hole on the outside where it matters.
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Old 09-15-2020, 12:36 PM   #36
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Peggie,
Iíve looked at Roncoís website and cannot find the size of the tank that requires replacement. The current tank is 48ĒL x 23 1/4ĒW x 9ĒH.
Any suggestions?
I had Ronco make me a custom tank a few years ago. They can make anything you want and place the number, size and placement of the fitting wherever you want as well.

Here is their custom order form:
https://ronco-plastics.com/wp-conten...m-2_081018.pdf

Instructions are at the bottom of this page:
https://ronco-plastics.com/product/w...-holding-tank/

You can call them and discuss directly as well. They will have someone call to discuss the tank diagram and what you're ordering anyway.
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Old 09-15-2020, 04:22 PM   #37
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Shrew, Ronco doesn't make one-off custom tanks unless the customer wants pay 'em to make a new mold for it, which would have cost you an extra "arm and a leg." So I'm 99.9% certain that you selected a tank from their catalog and then "customized" it by specifying the number of fittings, their locations and sizes.


And btw...if you take another look at Todd's post you'll see that he posted it in August of 2019.


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