Dip tube

Figment · Post by **Figment** » Tue Aug 07, 2007 7:47 pm

You knew this was coming, Tim. As soon as I got over the Summer of Sloth and got moving on boat projects again, a little bird clenched her talons into my shoulder and suggested that the holding tank ascend the priority list. As my great luck would have it, I notice you're back onto your tank for Kaholee.

What is that pvc fitting for the dip-tube, and is there anything involved in the installation beyond a nice gooey epoxy fillet?

Are you going to hose the pumpout to some remote location, or are you just going to locate the deck fitting directly over the pickuptube? I favor the latter for mine, it'll wind up about six inches inboard and aft of the upper shroud chainplate.

fusto · Post by **fusto** » Wed Aug 08, 2007 12:25 am

Ive found that this setup from Sealand works really well.
Cheap too. (~$27)

YMMV...

Post by **Tim** » Wed Aug 08, 2007 6:14 am

The fitting I used is simply a basic pipe to hose fitting. Because of availability concerns, mine has female threads on the bottom side (inside), so I use a slip-thread adapter to connect the PVC dip tube; if you have, or can get, a hose to slip fitting, that would be ideal. The extra fitting really isn't a problem here, since this is all sealed inside the tank. But it's nice to avoid if possible.

With only a 1/4" wall on the tank, there's plenty of barb remaining if I slip the fitting through from the inside and just goop it securely in place against the molded step in the fitting. I created a large fillet on the inside, and a small one outside.

The dip tube is just a length of PVC with an angle cut at the bottom, sized to end just above the bottom of the tank. But I'm sure you had that all figured out already.

I figured on running the pumpout hose more or less directly up. My location sounds about the same as yours, but perhaps a bit closer to the toerail based on where I located the tank discharge in the tank top.

Post by **Tim** » Wed Aug 08, 2007 6:16 am

fusto wrote:Ive found that this setup from Sealand works really well.
Cheap too. (~$27)

Does that fitting at the top accept PVC pipe or a male PVC fitting on the outside of the tank for eventual connection to the hose?

fusto · Post by **fusto** » Wed Aug 08, 2007 10:09 pm

Tim wrote:... or a male PVC fitting on the outside of the tank for eventual connection to the hose?

You got it.
Male PVC pipe at the top then to whatever you want after.

Sealand also makes a nifty PVC to 1.5" sani hose adapter.

Hirilondë · Post by **Hirilondë** » Sat Aug 11, 2007 12:44 am

I used that diptube kit from Sealand and the hose adapters for many head systems including several Sealand's VacuFlush. They all work with standard schedule 40 PVC. The dip tube with its rubber bushing will work in any material tank up to about 1/2" thick. Thicker than that will require some other type of waterproof installation.

Figment · Post by **Figment** » Sun Aug 12, 2007 7:40 pm

I'm going to hang back and wait for them to come up with one single fitting that is the dip tube, inlet, vent, and gauge.

Figment · Post by **Figment** » Thu Aug 16, 2007 7:33 pm

Ok, I didn't wait. I grabbed a SeaLand diptube kit that appeared on ebay.

Now that it's arrived, I can't remember the last time I was less impressed by a boaty-purchase. $7 worth of ordinary pvc and fittings that any monkey could have cobbled together in five minutes at the hardware store down the street. If I had paid anywhere near retail price, I'd be quite disgruntled.

Eh, it's here, so I'm over it. And I got to use the word "disgruntled". Time to make it work. :)

Dave, what's with this goofy rubber bushing? Why wouldn't I just permanently affix the top flange to the tank with some sealant and screws? Is there some virtue to the dip-tube being a friction-fit within this thing?

fusto · Post by **fusto** » Fri Aug 17, 2007 12:52 am

Figment wrote:Is there some virtue to the dip-tube being a friction-fit within this thing?

Easily removable if (when) the dip tube sucks up something bigger than it.

fusto · Post by **fusto** » Fri Aug 17, 2007 12:55 am

Figment wrote:$7 worth of ordinary pvc and fittings that any monkey could have cobbled together in five minutes at the hardware store down the street.

sigh...

I think the Sealand diptube is more geared to the boatyard or OEM installer.
At yard rates, the customer would have spent a lot more than the retail cost of the dip tube to have somebody (not a monkey) build one from scratch.
Might seem ridiculous, but thats the way it is.

Hirilondë · Post by **Hirilondë** » Fri Aug 17, 2007 8:38 am

Like Zachary said, the bushing is for easy removal. It also works well for use with polypropylene and such tanks where there is no good goop for sealing. I often make mock ups in cardboard, then have a plastic welder make me custom shaped poly tanks. I do agree Mike that it seems silly to pay so much for PVC pipe and fittings, but Sealand doesn't sell the fitting that fits into the bushing separately, and it isn't an otherwise available piece. You could buy the 2" Uniseal (the bushing made for 1 1/2" PVC pipe) and make your own diptube that is made from all standard 1 1/2" PVC and fittings and a Sealand hose adapter.

fusto wrote:I think the Sealand diptube is more geared to the boatyard or OEM installer.
At yard rates, the customer would have spent a lot more than the retail cost of the dip tube to have somebody (not a monkey) build one from scratch.
Might seem ridiculous, but thats the way it is.

Yup, when you factor in what customers pay for a system, the labor and the components, a few bucks saved trying to avoid a few over priced pieces costs more in the long run. Factor in also that as a certified VacuFlush installer I must use Sealand parts, and according to specifications, to maintain warranties.

Btw, install the bushing into the tank first, then use some liquid soap as a lubricant for getting the PVC into the bushing. No one is strong enough to force the piece in any other way. The soap works well with heat for getting the hose onto the adapters.

Figment · Post by **Figment** » Fri Aug 17, 2007 9:04 am

Hirilond? wrote: No one is strong enough to force the piece in any other way.

hmmmm that sounds like a dare to me!

Ceasar Choppy · Post by **Ceasar Choppy** » Fri Aug 17, 2007 9:22 am

slight hijack:

I've been looking for something much smaller than the sealand fitting to install dip tubes in my freshwater water tanks-- something on the order on 1/2 or 5/8. I've driven my self nuts trying to figure this one out, and I would gladly pay a premium for something like this (although I'm sure i would probably have the same buyers remorse Mike has once I paid for it!).

Anyone know of a pre-assembled dip tube assembly, smaller in size and safe for drinking water?

Hirilondë · Post by **Hirilondë** » Fri Aug 17, 2007 12:36 pm

Figment wrote:
Hirilond? wrote: No one is strong enough to force the piece in any other way.
hmmmm that sounds like a dare to me!

Hehe, I wish I could be there to watch you try.

Ceasar Choppy wrote:Anyone know of a pre-assembled dip tube assembly, smaller in size and safe for drinking water?

I know there are stainless seel diptubes with flanges that can be used on any tank that will seal well (not poly). They are used for fuel tanks mostly, but will work for water. I will check with the store manager at work monday for you Mike.

Ceasar Choppy · Post by **Ceasar Choppy** » Fri Aug 17, 2007 2:16 pm

Thanks Dave.

Hirilondë · Post by **Hirilondë** » Wed Aug 22, 2007 7:42 am

Two other commonly used terms for such parts are draw tube and pick up tube. Lewis Marine, a wholesale only company carries one that is for 1/2" hose model no. 6wta22 part no. 010270 that is 23" long and can be cut down to what ever. Any marine store should be able to order one for you Mike. Retail price is $17.26 and can have any hose barb or such fitting screwed into it as desired (extra). Any good boatyard store/parts dept. should be able to find what you want using the above 2 terms for a search. Good luck.

Ceasar Choppy · Post by **Ceasar Choppy** » Wed Aug 22, 2007 9:18 am

Dave,

really appreciate your help with this. Thanks!

Edit: I looked at these for my fuel tank... I guess I never thought of using a FUEL fitting for drinking water. LOL

Mike

Figment · Post by **Figment** » Wed Aug 29, 2007 12:59 pm

Just when I think I'm ready to install, another thought occurs.

I vaguely recall that The Headmistress recommends two vents for a holding tank. Aerobic decomposition, or some such thing. Does anyone actually do this? Should I bother adding a second vent?

Yes, of course, pics pics pics.

Figment · Post by **Figment** » Wed Aug 29, 2007 1:02 pm

and yes, Dave, I used soap to get the fitting into the rubber bushing.

I'm only mostly crazy, and as everybody knows, mostly crazy is also slightly sane.

Post by **dasein668** » Wed Aug 29, 2007 1:24 pm

Figment wrote:I'm only mostly crazy, and as everybody knows, mostly crazy is also slightly sane.

Hirilondë · Post by **Hirilondë** » Thu Aug 30, 2007 6:13 am

Figment wrote:Just when I think I'm ready to install, another thought occurs.

I vaguely recall that The Headmistress recommends two vents for a holding tank. Aerobic decomposition, or some such thing. Does anyone actually do this? Should I bother adding a second vent?

Yes, of course, pics pics pics.

The only time any real challenge is made on the vent of a holding tank is during pump out. I have seen imploded tanks due to how fast they remove the black water and that the air can't get in fast enough to replace it. I install a relief valve as well as a vent in all holding tanks.

http://www.travelerlite.com/productpages.asp?pid=68

bcooke · Post by **bcooke** » Thu Aug 30, 2007 10:09 pm

Had I thought about it in time I would have incorporated a second vent in the tank. What the heck, it can't hurt.

In my case, my tank was already welded up and installed before I came across that little gem of info. The next time I build a holding tank I will put two vents in it.

-Britton