Reply
 
Thread Tools Search this Thread Display Modes
 
Old 11-27-2018, 06:09 PM   #1
Senior Member
 
City: Texas
Country: USA
Vessel Model: 37' C&L Double Cabin
Join Date: Feb 2017
Posts: 154
connecting 2 tanks.... best option?

so as a followup to this thread Bladder or smaller poly tanks?

I ordered 2 50 gallon diesel tanks https://www.easternmarine.com/moelle...el-tank-032550

that's about the biggest tank I can get into the engine room without major trouble... and I can get 3 in there for the factory 150 gal capacity if I need to. this is all on the PORT side only for now.
So my question is: should I attempt to connect the tanks at the bottom to make one 100 gal fuel tank, or keep them separate?
If I connect them it's going to be complicated to add a fitting to the bottom of a Polyethylene tank... from my research I'll have to install a nut on the inside of the tank and possibly cut an inspection port to do so.
And if I keep them separate do I install a second deck fill? or have a selector valve for each tank and a Y?
also if they are separate I'll have to figure out the fuel pickup situation.
any help/advise is appreciated while I brainstorm and wait for tanks to come in.
Thanks
__________________
Advertisement

Nopistn is offline   Reply With Quote
Old 11-27-2018, 06:31 PM   #2
Senior Member
 
City: Texas
Country: USA
Vessel Model: 37' C&L Double Cabin
Join Date: Feb 2017
Posts: 154
also wondering if I could get the inside part of a bulkhead fitting through the fuel sender hole, or if anyone has had success doing this... I could imagine maybe using bailing wire to run the fitting down to the hole I've drilled in the bottom.
Attached Images
 
__________________

Nopistn is offline   Reply With Quote
Old 11-27-2018, 08:29 PM   #3
Senior Member
 
City: Texas
Country: USA
Vessel Model: 37' C&L Double Cabin
Join Date: Feb 2017
Posts: 154
a third option is maybe have one tank a day tank and one an AUX tank, with an electric transfer pump?
Nopistn is offline   Reply With Quote
Old 11-27-2018, 08:38 PM   #4
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 18,731
Just put a shutoff on each tank at the top feed and run one tank to a tee in the line from the second tank.

Each tank should have a shutoff anyhow, and the engine will only draw from whichever one you open.
psneeld is online now   Reply With Quote
Old 11-28-2018, 05:39 AM   #5
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 18,928
"Each tank should have a shutoff anyhow"

While its not a requirement for pleasure boats the Coasties demand a tank fuel cut f that can be controlled from outside the vessel for commercials .

Not many bucks for a safety that might save the vessel, or the usual huge fine if you put a teaspoon of diesel overboard and create an oil sheen.


Easy to do , just an outboard push pull cable when replacing tanks.
FF is offline   Reply With Quote
Old 11-28-2018, 06:03 AM   #6
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 18,731
The shutoff I believe is a ABYC suggestion (read insurance survey worthy) anyhow....

And it will allow separate uses of the 2 tanks.

AND if located to be accessed out of the engine room....like Fred posted.... BONUS.
psneeld is online now   Reply With Quote
Old 11-28-2018, 06:43 AM   #7
Guru
 
jleonard's Avatar
 
Join Date: Jun 2008
Posts: 3,250
The only time I saw twin replacement tanks they were either 50 or 55 gallon and they spaced about 1 foot apart (from memory) and they had a large, maybe 1 1/4 inch pipe connecting the bottoms, with a shut off in between.
Each tank had its own deck fill.
Both sides were set up this way.
__________________
Jay Leonard
Attitude Adjustment
40 Albin
Mystic,Ct. /New Port Richey,Fl
jleonard is offline   Reply With Quote
Old 11-28-2018, 06:55 AM   #8
Guru
 
Jeff F's Avatar
 
City: Great Lakes
Country: Canada
Vessel Name: Mazurka
Vessel Model: Mainship 34 Original
Join Date: Nov 2015
Posts: 569
What's your plan for fuel return? If you isolate the two you'll need to have dedicated valved return lines as well. I didn't see a return port mentioned in the specs.
Jeff F is offline   Reply With Quote
Old 11-28-2018, 07:29 AM   #9
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 18,731
If he has Lehman 120s, can't tell from pics in other thread...

They return so little fuel, I just plumbed them right back into the fuel feed lines at my fuel manifold with appropriate valves,zinced andey have worked for over 2000 hours that way just fine
psneeld is online now   Reply With Quote
Old 11-29-2018, 11:12 AM   #10
Senior Member
 
City: Texas
Country: USA
Vessel Model: 37' C&L Double Cabin
Join Date: Feb 2017
Posts: 154
Quote:
Originally Posted by psneeld View Post
If he has Lehman 120s, can't tell from pics in other thread...

They return so little fuel, I just plumbed them right back into the fuel feed lines at my fuel manifold with appropriate valves,zinced andey have worked for over 2000 hours that way just fine
Thanks for this! I was wondering if that would somehow interfere with the operation of the lift pump, or of the suction from the lift pump would interfere with the operation of the injection pump.
And yes they are FL120s
Nopistn is offline   Reply With Quote
Old 11-29-2018, 11:13 AM   #11
Senior Member
 
City: Texas
Country: USA
Vessel Model: 37' C&L Double Cabin
Join Date: Feb 2017
Posts: 154
Quote:
Originally Posted by Jeff F View Post
What's your plan for fuel return? If you isolate the two you'll need to have dedicated valved return lines as well. I didn't see a return port mentioned in the specs.
As the other poster said, I may just plumb the return back I to the feed. It's a FL120
Nopistn is offline   Reply With Quote
Old 11-29-2018, 11:15 AM   #12
Senior Member
 
City: Texas
Country: USA
Vessel Model: 37' C&L Double Cabin
Join Date: Feb 2017
Posts: 154
Quote:
Originally Posted by jleonard View Post
The only time I saw twin replacement tanks they were either 50 or 55 gallon and they spaced about 1 foot apart (from memory) and they had a large, maybe 1 1/4 inch pipe connecting the bottoms, with a shut off in between.
Each tank had its own deck fill.
Both sides were set up this way.
That would be a good option for me and simple IF I can figure out how to reliably make a 1" + outlet in the bottom of a polyethylene tank.
Nopistn is offline   Reply With Quote
Old 11-29-2018, 11:18 AM   #13
Senior Member
 
City: Texas
Country: USA
Vessel Model: 37' C&L Double Cabin
Join Date: Feb 2017
Posts: 154
Quote:
Originally Posted by psneeld View Post
Just put a shutoff on each tank at the top feed and run one tank to a tee in the line from the second tank.

Each tank should have a shutoff anyhow, and the engine will only draw from whichever one you open.
This is probably the simplest method and a second Y on the engine side of this for the return.
Nopistn is offline   Reply With Quote
Old 11-29-2018, 07:03 PM   #14
Guru
 
ben2go's Avatar
 
City: Upstate,SC
Country: USA
Join Date: May 2012
Posts: 1,755
From my understanding reading around here and the internets, it's better to not have any fittings low on the tank to prevent fuel leaks into the bilge and being pumped overboard by the bilge pumps. Am I wrong on this?
__________________


ben2go is offline   Reply With Quote
Old 11-29-2018, 07:19 PM   #15
Senior Member
 
TowLou's Avatar
 
City: Flanders, NJ
Country: USA
Vessel Name: Bassey
Vessel Model: 17' Bass
Join Date: Aug 2016
Posts: 163
Check out fuel systems in a big truck or MD market like a freightliner m2-106 with cross lines. I could fill one tank and it would balance out the level as well as handle the return flow.
TowLou is offline   Reply With Quote
Old 11-29-2018, 07:44 PM   #16
Guru
 
ben2go's Avatar
 
City: Upstate,SC
Country: USA
Join Date: May 2012
Posts: 1,755
Quote:
Originally Posted by TowLou View Post
Check out fuel systems in a big truck or MD market like a freightliner m2-106 with cross lines. I could fill one tank and it would balance out the level as well as handle the return flow.
None of the medium duty or commercial trucks I drove had that system. I've seen it though. Dumping 100 gallons of fuel on the ground doesn't seem as bad to me as dumping 100 gallons into a bilge and then overboard.
__________________


ben2go is offline   Reply With Quote
Old 11-29-2018, 07:53 PM   #17
Guru
 
AusCan's Avatar
 
City: Adelaide
Country: Australia
Vessel Name: Kokanee
Vessel Model: Cuddles 30 Pilot House Motor Sailer
Join Date: Jul 2012
Posts: 2,746
Quote:
Originally Posted by ben2go View Post
From my understanding reading around here and the internets, it's better to not have any fittings low on the tank to prevent fuel leaks into the bilge and being pumped overboard by the bilge pumps. Am I wrong on this?
There are differing opinions on this. I like to have a drain point at the lowest point on the tank. Preferably on a sump, but my present setup has the tanks sloping down to the drain point.

This bottom outlet valve is normally closed, and opened only to drain water, transfer fuel to the other tank, or check the level of either tank with the shared sight tube. This bottom drain point can also supply fuel to the engine in an emergency if the levels drop below the pickup tubes.

My fuel lines and fittings are heavy walled stainless steel rated at 6000 psi. A bit of overkill, but I think this system has much less risk of leaking fuel than a system with top fittings only but rubber or plastic fuel lines. You can still empty a tank into the bilge on top fitting systems if you develop a leak in your return line.
AusCan is offline   Reply With Quote
Old 11-29-2018, 09:23 PM   #18
Senior Member
 
TowLou's Avatar
 
City: Flanders, NJ
Country: USA
Vessel Name: Bassey
Vessel Model: 17' Bass
Join Date: Aug 2016
Posts: 163
Quote:
Originally Posted by ben2go View Post
None of the medium duty or commercial trucks I drove had that system. I've seen it though. Dumping 100 gallons of fuel on the ground doesn't seem as bad to me as dumping 100 gallons into a bilge and then overboard.
The freightliner I drove the M2-106 had a 40 gallon tank on driver side and a 60 gallon tank on the passenger side. Every other day I'd top off the passenger side and how they ran the fuel lines between the tanks it would balance out between the two with a cross system.
TowLou is offline   Reply With Quote
Old 11-30-2018, 07:00 AM   #19
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 18,928
"From my understanding reading around here and the internets, it's better to not have any fittings low on the tank to prevent fuel leaks into the bilge and being pumped overboard by the bilge pumps. Am I wrong on this?"

Simple to drain water from the lowest point in the tank.

The valve can be plugged as a second safety and a drain pipe installed only when checking for water & crud.

Personally I would not cross connect the tanks so a bad load of fuel could be kept isolated till cleaned.
FF is offline   Reply With Quote
Old 11-30-2018, 08:12 PM   #20
Senior Member
 
City: Texas
Country: USA
Vessel Model: 37' C&L Double Cabin
Join Date: Feb 2017
Posts: 154
Quote:
Originally Posted by AusCan View Post
There are differing opinions on this. I like to have a drain point at the lowest point on the tank. Preferably on a sump, but my present setup has the tanks sloping down to the drain point.

This bottom outlet valve is normally closed, and opened only to drain water, transfer fuel to the other tank, or check the level of either tank with the shared sight tube. This bottom drain point can also supply fuel to the engine in an emergency if the levels drop below the pickup tubes.

My fuel lines and fittings are heavy walled stainless steel rated at 6000 psi. A bit of overkill, but I think this system has much less risk of leaking fuel than a system with top fittings only but rubber or plastic fuel lines. You can still empty a tank into the bilge on top fitting systems if you develop a leak in your return line.
Your tanks are probably stainless as well them
I'm using polyethylene so I'm ot sure this applies.
__________________

Nopistn is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





All times are GMT -5. The time now is 08:16 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012