Mainship 400 waste holding tank replacement

[garmstro55]

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.

Take some photos along the way if you can, I'd like to see it visually!

 

[Stephen8]

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.

 

[HeadMistress]

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.

--Peggie

 

[Stephen8]

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.

 

[Comodave]

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.

 

[Shrew]

Peggie,
I’ve looked at Ronco’s website and cannot find the size of the tank that requires replacement. The current tank is 48”L x 23 1/4”W x 9”H.
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-content/uploads/2018/08/Ronco-order-form-2_081018.pdf

Instructions are at the bottom of this page:
https://ronco-plastics.com/product/water-waste-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.

 

[HeadMistress]

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.


--Peggie