Follow up on Holding Tank on Bene 381 (post 122281)

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Aug 30, 2010
12
Beneteau 381 Portsmouth, RI
This is a follow up to thread 122281

http://forums.oday.sailboatowners.com/showthread.php?t=122281

I worked over the winter with a number of folksand despite the ideas on this forum we elected not to move the tank location - everything is a compromise and we were not prepared to give up the closet space.

Nobody could find another location that did not involve unacceptable tradeof's - so we are going with the current location and I have now acquired a new Ronco tank, equipped as follows

(All in the TOP of the tank)

TWO 3/4" NPT female thermo-welded fittings for cross vents.

ONE 1 1/2" NPT female thermo-welded fitting for the "fill"

ONE 1 1/2" NPT female thermo-welded fitting for the deck pump out

ONE 1 1/2" NPT female thermo-welded fitting for the macerator pump out



Due to a miscommunication between me and the supplier these are standard 1 1/2" NPT female - I had asked for stand pipes and had not realized that I had to supply the actual stand pipe component that screws into the NPT and reaches towards the bottomofthe tank


Allmy fittings are on the top of the tank by design - No more drips AND no more effluent sitting in a pipe (provided I don't addany sags or dips when routing pipe.

So my questions :

Where do I buy the male NPT fittings to fit into my tank - are Todd any good ? What's the recommended brand here ?

How do I go about getting the stand pipe ? Do I buy a regular male NPT and glue a plastic pipe inside it ? How far off the botomof the tank should the bottomof this be? Should it be a square cut or should it be angled etc ?


I will be cross venting with 5/8" - They couldn't put 5/8" fittings in the tank hence the 3/4". Where can I buy fittings for the sides of the boat to vent these out ? I am positive what I have today are fuel fill fittings complete with gauze screens - This will be gone !

Any Yes - all new marine hose clamps, no goop - just teflon tape etc etc

Thanks in anticipation !

Mark
 
V

Velero 49

McMaster Carr

Try mcmaster.com...... What is the material of the tank? CPVC | Kynar (PVDF) | Nylon | Polypropylene | PTFE | PVC | UV-Resistant PVC?
 
Dec 2, 1997
8,946
- - LIttle Rock
Due to a miscommunication between me and the supplier these are standard 1 1/2" NPT female -

Which is what they should be. And if you hadn't had a breakdown in communication, Ronco would have supplied the male thread-barb fitting with the PICKUP TUBE already in it

However, this is an easy problem to solve with a piece of PVC pipe, some PVC cement and the right KIND of fitting,..which kind and where to get it depends on whether they need to be straight or 90.

So my questions :
Where do I buy the male NPT fittings to fit into my tank - are Todd any good ? What's the recommended brand here ?


When I know whether you need straight or 90 for the pickup tubes, I'll know whether you need SeaLand components or plain ol' plastic thread-barb fittings you'll find at any marine store.

How do I go about getting the stand pipe ? Do I buy a regular male NPT and glue a plastic pipe inside it ?

Yup...that's exactly what you do.

How far off the botomof the tank should the bottomof this be?

It should touch the bottom and be cut at about a 25 degree angle.

I will be cross venting with 5/8" -


I wouldn't....you have 3/4" fittings, that's the size your vent needs to be....and that's barely big enough to provide enough air flow to keep the tank aerobic.

They couldn't put 5/8" fittings in the tank ...

5/8" is the "standard" size vent for ALL tanks--fuel, water and waste...so that can't be true. But while 5/8" IS the standard tank vent sizes, no one took into account the idea that sewage--unlike water and fuel--must be managed, and 5/8" isn't big enough manage sewage aerobically. I'd have gone with 1"...So count your blessings that they installed 3/4" and that at least you spec'd two.

Where can I buy fittings for the sides of the boat to vent these out ?

At any marine store. What you need are "mushroom" or "bulkhead" fittings--Marelon, bronze or SS...but NOT nylon...and NOT "vent" fittings, which are all designed for fuel vents.

Btw...all PE water and waste tanks are LDPE, not HD. Only fuel tanks need to be HDPE, and they must be CLPE.
 
Aug 30, 2010
12
Beneteau 381 Portsmouth, RI
Hi Peggy

They are al 90's - I have about 6" of clearance atop the tank, as much as I would have liked to have had nice long radiused curves in the hoses, I can't.

Glueing a tube in to the 90 is what i thought - I have worked a lot with schedule 40 at home but my guess is that the polymers here may be different and the right kind of adhesive will be important. (NOt messing around here).

"Touch" and 25 degree - excellent !!! I assume the opening should face towards the main tank area and not into the corner.... right ?

Mushroom fittings are easy - I just ASSumed that I had to have one with the little clamshell on the outside - I have installed a number of regular mushroom vents before.

3/4" - straight hose without dips or kinks and venting to port and starboard - ( I hope I will get good cross ventilation for aerobic activity )
 
Dec 2, 1997
8,946
- - LIttle Rock
They are al 90's - I have about 6" of clearance atop the tank, as much as I would have liked to have had nice long radiused curves in the hoses, I can't.

Yes you can...you only need 5". And what you need are the SeaLand component fittings: SeaLand fittings Scroll to the bottom of the page to see the drawings. Glue the pickup tube into the threaded piece. Call SeaLand directly to order 'em: 800-321-9886

"Touch" and 25 degree - excellent !!! I assume the opening should face towards the main tank area and not into the corner.... right ?


Doesn't matter which way it faces.

Mushroom fittings are easy - I just ASSumed that I had to have one with the little clamshell on the outside - I have installed a number of regular mushroom vents before.

Then you should know that clamshell covers aren't integral to thru-hulls. Buy the ones you need to cover the size of the thru-hull.

3/4" - straight hose without dips or kinks and venting to port and starboard -

Correct.

Give me a shout if you need help.
 
Dec 2, 1997
8,946
- - LIttle Rock
Pickup tube can be any pvc...

I'd go with schedule 40. Cement it into the SeaLand #307341425 PVC adapter. Cement a 307341161 90 to that one and then 307341513 custom hose adapter. Warm the hose (be careful not to overheat it!) and use a little K-Y to slip it onto that one...secure with two hose clamps, screws 180 degrees apart...you're done. You'll have to order those fittings directly from SeaLand...they charge an arm and a leg for 'em, so I'd ONLY use 'em on the discharge fittings that need a pickup tube. Use the "standard" thread-barb fittings available at any marine store for the rest. Avoid 1.5" GRAY pvc. For some reason, the barb end is 1 5/8" OD, impossible to get 1.5" hose onto it.
 
Aug 30, 2010
12
Beneteau 381 Portsmouth, RI
Thanks Peggie

Bernie at North East Sanitation (Seland directed my query there) suggests p/n 342806 - a 90 degree 1.5" fitting, but he does not have a photo of it.
 
Dec 2, 1997
8,946
- - LIttle Rock
I found it...it's just a thread-barb PVC elbow, like any you can find at any marine store, just costs a lot more. It's a good suggestion, 'cuz it eliminates the need for all that PVC cement. Or...you can go with ANY thread-barb 90.

Tell the guy at NE Sanitation he can find an illustration of it if he looks in the exploded drawing on page 8 of the instructions for the SeaLand "holding tank kit."

I would NOT use one of SeaLand dip-tube kits, for two reasons: 1. it's not designed for use in a threaded female tank fitting, and ...2. The price is about 5x what it costs to assemble the same parts to make one.
 
Oct 2, 2007
131
- - Millville, NJ
Regarding 5/8" vent line fittings...

RONCO and most other plastic tank manufacturers only supply their spin-welded female collar fittings in standard U.S. (NPT) pipe thread sizes. THERE IS NO 5/8" U.S. PIPE THREAD SIZE.

So, as a matter of course, they'll step it up to 3/4" pipe thread. If you must have a 5/8" I.D. vent line, which isn't recommended, there are adapters to go from 3/4" pipe thread to 5/8" hose barb, which are readily available at any good hardware store.

But don't run to West Marine or Land N Sea, expecting to find the necessary vent line adapters to accomodate 5/8" I.D. hose - you won't find 'em there. Go to a good hardware store - the old-fashioned Mom N' Pop places are usually the best - and usually the cheapest. And avoid metal adapters. PVC, Marelon and nylon are all OK for the vent line adapters, as long as they won't be exposed to UV rays.
 
Dec 2, 1997
8,946
- - LIttle Rock
Butbutbut...

RONCO and most other plastic tank manufacturers only supply their spin-welded female collar fittings in standard U.S. (NPT) pipe thread sizes. THERE IS NO 5/8" U.S. PIPE THREAD SIZE.
In all the years we sold Ronco tanks, we specified a LOT of 5/8" vents, mostly on water tanks (and a few holding tanks for customers who couldn't be convinced that bigger is better). They never told me they couldn't do it or stepped it up without telling me...so they must have stepped 'em DOWN to 1/2"--which would make sense if the threaded end of a fitting is 1/2" OD and the barbed end is 1/2" ID, making the OD 5/8"...'cuz standard 5/8" vent fittings always fit 5/8" vent hose.

Till just now I always thought that the difference in the sizes of the threaded end and barbed end of the 1.5" gray PVC fittings was ONLY true of 1.5"...but this makes me think it may be true of ALL gray PVC thread-barb fittings.
 
Oct 2, 2007
131
- - Millville, NJ
Re: Butbutbut...

Peg, you could very well be right about scaling the fitting size DOWN to ½”, rather than scaling it UP to ¾”, to accommodate a 5/8” hose barb to attach a 5/8” I.D. vent hose. American pipe sizes and dimensions are kind of weird. The outer diameter of a nominal ½” pipe, is .840”. The outer diameter of a ¾” pipe is 1.050”. So an adapter with a ½” pipe thread at one end could easily accommodate a 5/8” (.625”) hose barb at the other end, there’d certainly be enough material to do it that way. But in all of my holding tank applications where a 5/8” vent line is called for, I always scale the fitting up to ¾” to allow more flexibility, but that’s just me. There’s no reason it couldn’t be a ½” pipe thread at one end and a 5/8” hose barb at the other end, with a 1/2” female pipe thread in the tank.
 
Aug 30, 2010
12
Beneteau 381 Portsmouth, RI
So I received my parts from Sealand and tested one for fit - very nice. I then set about constructing dip tubes with a 25 degree cut on the bottom and they came out nice. This weekend I installed and strapped the tank and began to put my fittings in - Doh !! what I missed was with three 1.5" NPT fittings in the top of the tank I cannot install 90 degree fittings, the L on the fitting fouls the one next to it. Fortunately I have more room than I thought above so I can install a straiht fitting with a gradual bend in the pipe.

So I dashed down to West Marine and picked up a 1.5" Marelon straight fitting - the odd thing is the threads don't seem to match - I took it back and bought two - same results - the threads are not a good fit - they seem to bind after a couple of turns (not cross threaded) - they certainly don't screw in anywhere as nicely as the Sealand fittings.

Is there a better choice of vendor for the 1.5" straight fittings ?

Thanks

Mark
 
Dec 2, 1997
8,946
- - LIttle Rock
May not be a problem...

Tank fittings should only be tightened just ONE turn past hand tight...because NPT is slightly tapered, any more than that risks cracking the female "collar."

You're saying just a couple of turns...that may be enough if they're wrapped in teflon tape.

If that's not the answer, try nylon. Or, go with a straight SeaLand fitting.
 
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