Reply
 
Thread Tools Display Modes
 
Old 07-01-2014, 11:35 AM   #1
Senior Member
 
sum escape's Avatar
 
City: Muskegon, MI
Country: Cruising
Vessel Name: Sum Escape
Vessel Model: Grand Banks 47' Europa
Join Date: Jun 2014
Posts: 133
Fresh Water Tanks- Balance Line

Cannot get water tanks to "balance". I have 2 tanks, one forward low in the hull and one aft mounted higher in the lazarette . They are tied together with a line with a valve at each tank, so that the aft flows into the forward as it empties to the fresh water pump. Air vents are clear to both tanks, valves operate and are clear, I can force water from aft to forward tank with garden hose, but forward tank empties and aft is still full. The top of the aft tank is at least 2-1/2 feet above the top of the forward tank so there should be significant head pressure to feed the forward tank. This is defying the laws of physics and makes no sense to me.....
Can anyone provide any direction for me on this? Some sort of air lock? Tricks or tips are welcome! Thanks!
__________________
Advertisement

sum escape is offline   Reply With Quote
Old 07-01-2014, 12:52 PM   #2
Guru
 
Capt.Bill11's Avatar
 
City: Sarasota/Ft. Lauderdale
Country: USA
Join Date: Apr 2014
Posts: 5,422
The line that ties the two tanks together, does it go directly from each tank with nothing in between? Or does it go through a manifold or something?

If you empty the fwd tank and fill the aft tank no water goes into the the fwd tank from the aft tank at all?
__________________

Capt.Bill11 is offline   Reply With Quote
Old 07-01-2014, 12:57 PM   #3
Senior Member
 
sum escape's Avatar
 
City: Muskegon, MI
Country: Cruising
Vessel Name: Sum Escape
Vessel Model: Grand Banks 47' Europa
Join Date: Jun 2014
Posts: 133
Quote:
Originally Posted by Capt.Bill11 View Post
The line that ties the two tanks goes directly from each tank with nothing in between? Or does it go to a manifold or something?
Diagram in owners manual just shows the balance line with valves at each tank. No manifold in diagram.
sum escape is offline   Reply With Quote
Old 07-01-2014, 01:04 PM   #4
Guru
 
Capt.Bill11's Avatar
 
City: Sarasota/Ft. Lauderdale
Country: USA
Join Date: Apr 2014
Posts: 5,422
Quote:
Originally Posted by sum escape View Post
Diagram in owners manual just shows the balance line with valves at each tank. No manifold in diagram.
That's what the diagram shows. But what is the reality? :-)

When you say you can force water from the aft tank to the fwd tank with a water hose it sounds like you need pressure to over come a restriction.

Did the tanks ever balance? There isn't a water manifold on the fwd engine room bulkhead by any chance?
Capt.Bill11 is offline   Reply With Quote
Old 07-01-2014, 01:23 PM   #5
Senior Member
 
sum escape's Avatar
 
City: Muskegon, MI
Country: Cruising
Vessel Name: Sum Escape
Vessel Model: Grand Banks 47' Europa
Join Date: Jun 2014
Posts: 133
Quote:
Originally Posted by Capt.Bill11 View Post
That's what the diagram shows. But what is the reality? :-)

When you say you can force water from the aft tank to the fwd tank with a water hose it sounds like you need pressure to over come a restriction.

Did the tanks ever balance? There isn't a water manifold on the fwd engine room bulkhead by any chance?
Just bought boat in last two weeks so do not know all the systems too well yet. Thus I cannot answer either question. I can manually blow bubbles into aft tank from forward tank when the line is removed from the valve (without a lot of effort) and water would flow from aft to forward tank under garden hose pressure.
I will trace the line through the ER and see if I find a manifold or some other restriction next time I visit the boat later this week.
Thanks much for the suggestions.
sum escape is offline   Reply With Quote
Old 07-01-2014, 01:44 PM   #6
Guru
 
City: gulf coast
Country: pinellas
Join Date: Jun 2014
Posts: 2,199
Also look for a high loop.
bayview is offline   Reply With Quote
Old 07-01-2014, 01:57 PM   #7
Guru
 
Capt.Bill11's Avatar
 
City: Sarasota/Ft. Lauderdale
Country: USA
Join Date: Apr 2014
Posts: 5,422
Quote:
Originally Posted by bayview View Post
Also look for a high loop.
That was my next comment. The pressure from the water hose may be pushing water up hill.

On a lot of GBs the water tanks go to a manifold system where you pick which tank the pump draws from. And while you can open the valves at the manifold to connect two tanks together they may not balance out and the pump may not draw from both tanks equally at the same time.
Capt.Bill11 is offline   Reply With Quote
Old 07-01-2014, 02:03 PM   #8
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 15,881
Are you absolutely sure that tank is 2.5 feet higher..or are you going by interior reference points like deck levels, counters, etc?

The interior of my boat has so may optical, illusions, for lack of a better word....it's impossible to tell what is actually higher when worried about trim, gravity, flow, etc...

one way to tell for sure is use a water level...a length of hose filled with water where both ends are clear so you can see the water level. You can quickly check the exterior of the tanks to see how close they are and that may help to determine if you have a hidden high loop or a restriction.
psneeld is offline   Reply With Quote
Old 07-01-2014, 02:28 PM   #9
Guru
 
City: Tuckerton, NJ
Country: USA
Vessel Name: WIRELESS ONE
Vessel Model: 36 Gulstar MarkII
Join Date: Mar 2011
Posts: 937
Quote:
Originally Posted by psneeld View Post
Are you absolutely sure that tank is 2.5 feet higher..or are you going by interior reference points like deck levels, counters, etc?

The interior of my boat has so may optical, illusions, for lack of a better word....it's impossible to tell what is actually higher when worried about trim, gravity, flow, etc...

one way to tell for sure is use a water level...a length of hose filled with water where both ends are clear so you can see the water level. You can quickly check the exterior of the tanks to see how close they are and that may help to determine if you have a hidden high loop or a restriction.
That's a great way to see what is really level.
Bill
Billylll is offline   Reply With Quote
Old 07-01-2014, 08:15 PM   #10
Guru
 
twistedtree's Avatar
 
City: Gloucester, MA
Country: USA
Join Date: Jan 2013
Posts: 3,187
I have the same boat and have experienced the same issue. Be absolutely certain that your vents are clear. Other than removing the vent line at the tank and blowing out, I don't know how else to verify. I often get a girggling sound from my vent lines. If the vents have any water in them it will create enough back pressure to prevent flow from the aft tank to the forward tank.

One easy way to test for vent back pressure is to open the deck fill caps for both tanks. That will provide super-venting. Then go down and open the hatch over the forward tank and listen to see if you hear water flowing. I'll bet that you will with the fill caps off. If it flows with the caps off, then you have vent blockage. Note that ANY water in the vent line will prevent balancing.

On my boat the vent line for the forward tank runs pretty much horizontal under the floor, then up behind the stateroom locker. That horizontal portion floods when both tanks are full because it is below the level of the aft tank. If it has any low spots or sags, it's prone to air locking.
__________________
www.MVTanglewood.com
twistedtree is offline   Reply With Quote
Old 07-02-2014, 07:37 AM   #11
Senior Member
 
sum escape's Avatar
 
City: Muskegon, MI
Country: Cruising
Vessel Name: Sum Escape
Vessel Model: Grand Banks 47' Europa
Join Date: Jun 2014
Posts: 133
Thanks so much. That makes perfect sense. I tested the aft air vent (all clear) but will have to test the forward air vent when I get to the boat this weekend. Sounds like the trick is to never overfill and get water in the vent lines. Sometimes one gets lazy and just lets the water overflow to know its full....bad idea! :>)
PS Beautiful new Norhavn!! Wow! Congratulations.
sum escape is offline   Reply With Quote
Old 07-02-2014, 07:49 AM   #12
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 15,881
Quote:
Originally Posted by sum escape View Post
Thanks so much. That makes perfect sense. I tested the aft air vent (all clear) but will have to test the forward air vent when I get to the boat this weekend. Sounds like the trick is to never overfill and get water in the vent lines. Sometimes one gets lazy and just lets the water overflow to know its full....bad idea! :>)
PS Beautiful new Norhavn!! Wow! Congratulations.
The vent lines if set up properly, they often warn you the tank is full...

....also not quite sure why letting a properly set up system being overfilled should be a problem...

I have seen examples where they are not, but most are reasonably easy to be fixed.
psneeld is offline   Reply With Quote
Old 07-02-2014, 08:03 AM   #13
Guru
 
City: Tuckerton, NJ
Country: USA
Vessel Name: WIRELESS ONE
Vessel Model: 36 Gulstar MarkII
Join Date: Mar 2011
Posts: 937
I'd rather have the tanks filled to the brim than run out of water because I was worried about the tanks balancing? Maybe it's just me?
Bill
Billylll is offline   Reply With Quote
Old 07-02-2014, 08:21 AM   #14
Senior Member
 
sum escape's Avatar
 
City: Muskegon, MI
Country: Cruising
Vessel Name: Sum Escape
Vessel Model: Grand Banks 47' Europa
Join Date: Jun 2014
Posts: 133
Quote:
Originally Posted by Billylll View Post
I'd rather have the tanks filled to the brim than run out of water because I was worried about the tanks balancing? Maybe it's just me?
Bill
The problem is the forward tank empties (160 gal) and the aft tank (100 gal) is still full when this air lock occurs as the pump draws only from the forward tank. Now that I know how to fix it (I think) I'd rather "short fill" by 20 gals than have to deal with clearing lines to get it to balance. Perhaps I will find a "low spot" in the vent and can correct the situation as well. Thanks
sum escape is offline   Reply With Quote
Old 07-02-2014, 08:28 AM   #15
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 15,881
Quote:
Originally Posted by sum escape View Post
The problem is the forward tank empties (160 gal) and the aft tank (100 gal) is still full when this air lock occurs as the pump draws only from the forward tank. Now that I know how to fix it (I think) I'd rather "short fill" by 20 gals than have to deal with clearing lines to get it to balance. Perhaps I will find a "low spot" in the vent and can correct the situation as well. Thanks
If not...how about a draw from the aft tank to the pump? ...that is if you don't find an easy solution to your problem....

I just finished redoing my entire fresh water system with pex. Moved the pump, tank feed lines, and water heater.

The who thing was simple (not a leak 1st time pressurized) other than crawling around the bilge, inexpensive and made the whole system easier to access and with cutoffs at every fixture now (instead of none)...I can change out or work on anything without taking the whole boat down.

Not saying redo the whole system...just add another feed that would give you what you need and give you ideas that may help improve your whole system.
psneeld is offline   Reply With Quote
Old 07-02-2014, 08:46 AM   #16
Senior Member
 
sum escape's Avatar
 
City: Muskegon, MI
Country: Cruising
Vessel Name: Sum Escape
Vessel Model: Grand Banks 47' Europa
Join Date: Jun 2014
Posts: 133
Something to think about if I cannot find an easy fix. Pump is close to aft tank in the lazarette so probably not too difficult. Thanks for your thoughts.
sum escape is offline   Reply With Quote
Old 07-02-2014, 11:19 AM   #17
Guru
 
twistedtree's Avatar
 
City: Gloucester, MA
Country: USA
Join Date: Jan 2013
Posts: 3,187
Wow, your pump is in the laz? Mine is on the forward bulkhead of the ER.

Anyway, there is no way around flooding at least part of the forward vent line. With the balancing line open, the water level in the forward tank's vent line will rise to the level of the aft tank, which on my boat is about 6-10" below the cockpit deck, and a good 3' above the forward tank's top. The result is that the portion of the vent line that runs along the underside of the forward sole always floods when you fill the tanks. The problem appears to be that it has inadequate slope to reliably drain back into the forward tank. This is probably hard to visualize without knowing the boat, but I'm doing my best to describe it. To be it's a bit of a design weakness in the boat, but correctable to an acceptable level. Unlike sum escape, I only get about 20 gal stranded in the aft tank which is a small portion of the 260 gal total water capacity. If I open the deck fills, the stranded 20 gal eventually work there way forward, but I only bother to do it as part of winterizing. Boat trim due to fuel, tender, etc will also have an impact. It would certainly be possible to touch up the slope of the vent line, and that might be what sum escape needs to do, but I'd confirm the problem by removing the deck fills and confirm that the water flows forward as expected. That will prove that it's a forward vent issue.
__________________
www.MVTanglewood.com
twistedtree is offline   Reply With Quote
Old 07-02-2014, 11:35 AM   #18
Senior Member
 
sum escape's Avatar
 
City: Muskegon, MI
Country: Cruising
Vessel Name: Sum Escape
Vessel Model: Grand Banks 47' Europa
Join Date: Jun 2014
Posts: 133
twistedtree,
That is the plan....open both fill caps and see if we get a balance line flow. Then work from there. Not sure if PO had this issue and may reach out to them as well. Thanks again for the input.
__________________

sum escape is offline   Reply With Quote
Reply

Thread Tools
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 10:16 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012