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kenstrom
Last seen: 4 months 2 weeks ago
Joined: 2/5/09
Posts: 65
Swolen Water Tanks

I just commissioned my 2004 C36MKII.  As part of normal process, I flushed out all three water tanks from anti-freeze, a couple of partial rinses, a weak bleach solution and let sit for three hours, full drain, a few more partial rinses and then filled with clean water.  I opened bow tank supply valve and kept two aft tank valves closed.

Nnext day I noticed a wood panel under aft berth was raised.  I removed panel and a starboard aft tank had "swelled" and was about 2 inches higher than normal.  Looked like it could have burst almost.

I opened the valve from aft starboard tank to the water supply pump and tank returned to normal after running a few gallons down drain.

So I'd appreciate any help on these questions.

- Don't all three water tanks have breather vents?  If not, we would get a suction when tyring to use tank, right?

- How could pressure have been created in tank?  I just filled with clean water and then screwed in the deck fill cover.

Ken Enstrom
2004 C-36 MKII #2199
Tall Rig, Wing Keel, M-35B
S/V Valkyrie - Sail Great Lakes

--

Ken Enstrom
2004 C-36 MKII #2199
Tall Rig, Wing Keel, M-35B
S/V Valkyrie - Sail Great Lakes

jmcelwee
Last seen: 2 years 3 days ago
Joined: 7/16/12
Posts: 102

Hi Ken,

 

Yes, all 3 tanks should have breather vents.  That said, they can get blocked, and you should check that the vent/line for that tank is clear.  I've had similar things happen when my vent lines aren't clear.

 

 

--

Josh McElwee
Sailing from East Greenwich, RI
2000 C36 MKII, M35B, "Chinook", Hull#1900

rtrinkle's picture
rtrinkle
Last seen: 2 months 2 weeks ago
Joined: 10/14/12
Posts: 203

I to have seen this. My 2 aft tanks use the same breather vent. There was some water still in the line. Once I blew it out, everything was fine. I would recommend filling the starboard aft tank before filling the center tank.  I also noticed a sharp kink in the breather hose where it attaches to the transome. I cut the kink out and re-attached. Seems to be breathing better.  Soon, I will also check the rise and run of the hose, and ensure there is no place for it to trap water. 

--

Robert Trinkle
Troubador, 1995 C36 MKII #1433, SR/WK
Universal M35A
Kinsale Harbor Marina
Kinsale, VA

BudStreet
Last seen: 1 year 4 months ago
Joined: 9/4/09
Posts: 1127

This problem has been kicked around for a while, pretty sure there's other posts on the forums about it.  Essentially it seems the shared vent on the aft tanks doesn't work very well and allows both tanks to get overfilled.  I have on my list for next winter's work to add a 2nd vent and hope that helps.  It doesn't seem to harm the tanks though I think over time it can't be good for them.  The front tank also will do this, you just don't notice it because it does't affect anything visible without taking the cover off, so it could be the problem actually is too small a vent to keep up with incoming water flow.

newguy's picture
newguy
Last seen: 5 months 1 week ago
Joined: 8/1/11
Posts: 408

Clearly you have an vent issue. If the vent is shared, when you fill the first tank and move to the second tank and if you stuck the hose into the filler neck and overfilled the second tank, it would pressurize the first tank (via the vent). It would indeed stay like that if the vent line was clogged downstream of where the two vent lines merge, i.e, between the "tee" and the transom vent. That's the only way I could see the situation happening, so check for a clogged vent between the tee and the transom fitting. 

BTW, some hose ends almost make a complete seal in the filler neck and the hose threads lock the host in to some degree. If you stuff the hose end into the filler neck with full blast water, you run the danger of temporarily pressurizing your water tanks when they get full, even with a proper vent system because the volume of water (not air) that the vent can drain upon overfill is much less than a 5/8" hose with city pressure can deliver.

--

Nick Caballero
Retired C36/375IA Mk II Technical Editor

plaineolde's picture
plaineolde
Last seen: 2 years 9 months ago
Joined: 11/4/08
Posts: 753

My vent is clear, spits water, yet the tank will still bulge.  Always has.   My boat has 3 vents by the transom walkthrough, so I don't think any are shared (2 tanks, one propane locker).   I've never understood how the tank can spit water and air, I turn off the hose and let the water in the fill tube settle, then go check the tank and it' bulging.   Hard to believe that the weight of the water in the fill and vent hoses are enough to bulge the tank, you'd think the tank would just push the excess water out of either of those hoses.   

Strange.

--

Gary and Cathy Price
1997 C36 Mk II Tall Rig/Wing Keel Imagine...
Hull # 1617
Worton Creek, Md.
Northern Chesapeake Bay

mccartyj's picture
mccartyj
Last seen: 2 years 7 months ago
Joined: 7/20/11
Posts: 21

My vent is clear, spits water, yet the tank will still bulge.  Always has.

Me too, this was pointed out to me when I bought my boat by the surveyer.

The tank deforms when it is full.

It is so tighly enclosed that it will dislodge the hatch cover as mine did.  

I have found the easy solution to be; fill the tank, go below and run about 5 gallons out into the galley sink. Done.

If the system was pressurized you would know when you took the the fill cap off by the escaping water or air. Not likely. 

--

Iti Motu
2006 MK ll
M35 BC,
Standard Rig w/LeisureFurl Boom
Flex-o-fold 3 blade 15/9
Rocna 15
Sail #2263

newguy's picture
newguy
Last seen: 5 months 1 week ago
Joined: 8/1/11
Posts: 408

I'll have to take a look at mine the next time I fill up. Seems to defy the laws of physics somewhat, i.e., a non-pressurized water tank can convex a side that does not even have the weight of water acting on it. I can understand convexing the other 5 sides which would seem natural then to concave the top side.  Fair to note that my understanding of the laws of physics have been shaken lately..... http://en.wikipedia.org/wiki/Sailing_faster_than_the_wind#Sailing_dead_d...

--

Nick Caballero
Retired C36/375IA Mk II Technical Editor

mccartyj's picture
mccartyj
Last seen: 2 years 7 months ago
Joined: 7/20/11
Posts: 21

Seems to defy the laws of physics somewhat, i.e., a non-pressurized water tank can convex a side that does not even have the weight of water acting on it.

I agree, sounds impossible and very counterintuitive. And I'm no physicist either.

From my observations this is what appears to be happening. As you fill the tank the weight of the water makes the sides of the tank want to go round slightly. This includes the bottom. So when the tank is full the bottom of the tank is no longer completely flat. This pushes the whole tank up slightly. In my case the fit is so tight on the top side it actually pushed the screws out that were holding down the hatch cover.

It's never a problem as long as I don't fill the tank to the top.

But...I could be wrong.

--

Iti Motu
2006 MK ll
M35 BC,
Standard Rig w/LeisureFurl Boom
Flex-o-fold 3 blade 15/9
Rocna 15
Sail #2263

LCBrandt's picture
LCBrandt
Last seen: 2 months 2 weeks ago
Joined: 6/26/07
Posts: 1282

Not a vent issue, but simply gravity at work. (An internet search for Isaac Newton will yield more details.)

The tanks bulge. After filling my tanks I run off some water from each into the galley sink until everything settles back to normal. The only real problem with this is that the tank inspection vents can leak, causing an overflow of fresh water into the bilge. I solved that issue by placing a small bead of 3M 5200 around the threads of the tank inspection cap. 

I never tie tanks together at the valves. I always use each tank independently until each runs dry, and I usually begin with the bow tank first - to take weight out of the bow.

--

Larry Brandt
S/V High Flight #2109
Pacific Northwest, PDX-based
2002 C-36 mkII SR/FK M35B
 

kenstrom
Last seen: 4 months 2 weeks ago
Joined: 2/5/09
Posts: 65

Thanks for all of the help and comments.

I just had time to inspect and fix my problem.  I have two separate air vents on my transmission -- one for each aft tank.  I again topped off both aft tanks with water and noticed that water slowly dribbled out of the stbd tank that I had trouble with, but water freely ran out of the center tank vent.

I removed the air vent line from the stainless steel vent fittings on the transom for the stbd tank. It appeared to be clear.  Then I removed the metal fitting from the transom and had a hard time blowing air through it.  After using a high pressure hose blowing water through the screens in the reverse direction I was able to remove all the sediment, etc.

Problem solved.  I had a pluged metal vent fitting on the stbd tank.

--

Ken Enstrom
2004 C-36 MKII #2199
Tall Rig, Wing Keel, M-35B
S/V Valkyrie - Sail Great Lakes

Backwater's picture
Backwater
Last seen: 3 weeks 3 days ago
Joined: 8/10/14
Posts: 11

I've just experienced an identical problem! Will pull apart the transom vent assembly tomorrow! Thanks! The aft starboard tank needs a new vent elbow fitting. Anyone know a good supplier?

Channel Islander's picture
Channel Islander
Last seen: 14 hours 51 min ago
Joined: 10/8/11
Posts: 378

Hi Backwater, and welcome to the site!

Many people use Defender (defender.com) as having as a good a selection as West Marine, and better prices. I also read recently that they are a good option for shipping parts overseas (this was to Mexico) because they paste and invoice with pricing on the exterior of the package, which helps get through customs more easily. I see that your C36 is in Dubai, so maybe that's useful information.

For Catalina-specific parts many people use catalinadirect.com as well as the factory directly. There are countless sources. You will learn a lot from these forums, and I urge you to also join the International Association as a Member, which will give you access to the Technical Library, and, if you join for three years as a full Member, a copy of the Tech Notes CD with Mainsheet technical articles back to 1984, more than 45 owner manuals, the owner manual for your boat and engine, and much more.

Welcome!

--
Nick Tonkin
*Former* Website Administrator, C36/375IA
*Former* owner, C36 tr/fk #255, Santa Barbara, CA
Backwater's picture
Backwater
Last seen: 3 weeks 3 days ago
Joined: 8/10/14
Posts: 11

 
Hi Nick, and thanks for the warm welcome. I'm into my second year as the proud owner of Wanderlust and the learning curve shows no sign of flattening out! I'll give Defender a go thanks. Dubai is a difficult place to maintain a US boat, the tyranny of distance and time zones - I recently went through a water heater replacement, bought a nice Seaward product but omitted to order NPT fittings. Eventually had them made - that happens a lot out here - a lot of ingenuity required! 

All the best. I guess you'll see a lot of me in the coming years!
Craig

mutualfun's picture
mutualfun
Last seen: 8 months 4 weeks ago
Joined: 6/25/07
Posts: 454

Been thru the vent issue years ago. Cleaned them, replaced them ect. The tanks are made by Ronco and are not that thick. The weakest side is the top. So naturally that will bulge and unseal the cap which leaks water. What we did and have never had a issue sense was to build a removable wood top to all our tanks which will not let the tanks expand nor leak via the tank cap. Now when full the water just exits the air vents vents.

--

Randy Sherwood
Mutualfun 1990 # 1057
T/R W/K M35a
Home. Charlotte, Mi.
Boat. St Augustine,Fl.

GaryB's picture
GaryB
Last seen: 1 day 8 hours ago
Joined: 10/26/08
Posts: 520

Randy,
Can you explain what you mean by (was to build a removable wood top to all our tanks which will not...) not sure I understand what you did. Replace the whole top?

--

Gary Bain
S/V "Gone With The Wind"
Catalina 36', Hull #: 1056, Year: 1990, Engine: M-35
Standard Rig
Moored: East Boothbay, Maine
Home: Auburn, Maine

mutualfun's picture
mutualfun
Last seen: 8 months 4 weeks ago
Joined: 6/25/07
Posts: 454

Gary.
On our 1990 I am able the get access to the top of our water tanks. So what I did was I took and bult wood tops that were held in by screws as it held the tops down from bulging and the caps from leaking. Our's use to leak with the old style caps that had no flat seal. So I bought the new style tank caps from Ronco but then I had file down the 4 little plastic risers so the new cap would seal. But those even leaked as the tanks would still swell. So what I did was built wood tops that held the top of the tanks down from bulging with access holes for the caps. After I did this the caps never leaked and once filed the water would squirt out of the vents. Hope this clears things up

--

Randy Sherwood
Mutualfun 1990 # 1057
T/R W/K M35a
Home. Charlotte, Mi.
Boat. St Augustine,Fl.

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