Losing water in holding tank.... help

Cant Wait

Cant Wait

New Member
Jan 2, 2012
26
Knoxville, TN
Boat Info
41 Sundancer 2000
Engines
454 twin engines..
I filled up the holding water tank 100 gallons and has always worked great. This past weekend i turned on the water heater for the first time this year and after a few hours my water tank was empty... I mean no water anywere at all. I checked for leaks and the boat is bone dry. Filled it up again and went out all day and worked fine when water heater was turned off. Turned it on and 4 hours later boat had no water again???? I cant see were it is going. I stayed in a cove and keep looking for it coming out and never saw it anywere. Any ideas i mean 200 gallons of water cant just run away lol.. Any how any help would be great. I never saw or heard the bilge pumping it out etc..
 
Put food grade color dye in the water tank. It should show up some place.
 
Have you checked the anchor washdown spigot? If it's not fully closed, it will send water out the anchor locker drains at the bow, which is easy to miss.
 
Cant Wait said:
I filled up the holding water tank 100 gallons and has always worked great. This past weekend i turned on the water heater for the first time this year and after a few hours my water tank was empty... I mean no water anywere at all. I checked for leaks and the boat is bone dry. Filled it up again and went out all day and worked fine when water heater was turned off. Turned it on and 4 hours later boat had no water again???? I cant see were it is going. I stayed in a cove and keep looking for it coming out and never saw it anywere. Any ideas i mean 200 gallons of water cant just run away lol.. Any how any help would be great. I never saw or heard the bilge pumping it out etc..
Click to expand...

The most confusing part of your explanation is "...Filled it up again and went out all day and worked fine when water heater was turned off..."

What having HWH ON or OFF has to do with having water present or disappearing? All that switch does is activating HEATING ELEMENTS to heat up the water in the HWH, but it has nothing to do in regards to the volume of water. Perhaps you were talking about FRESH WATER PUMP switch?
 
That might be the pressure relief valve in the water intake (where you connect the fresh shore water) in transom hatch, my 280's failed
 
RollerCoastr said:
Have you checked the anchor washdown spigot? If it's not fully closed, it will send water out the anchor locker drains at the bow, which is easy to miss.
Click to expand...

trade wins said:
That might be the pressure relief valve in the water intake (where you connect the fresh shore water) in transom hatch, my 280's failed
Click to expand...

I'll bet it is one of these two.
 
Another option is the pressure valve - the one at (on) the hot water tank, itself (just like on a home hot water tank). There is a black, rubber hose attached to it - it usually empties out the side of the hull. These don't fail too often, but if the lever got bumped (or left) into the open position, it will stay there.
 
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I was filling my water tank 3 times a weekend. I couldn't figure out where the water was going. It turns out that the pressure relief valve on the water heater was stuck and leaking. There must be some kind of check valve in the system so that whenever someone used the water, most of it was being pumped out the side of the boat! A new relief valve fixed this... got it at an RV parts supplier.
 
I bet you 2 beers that it is the pressure relief valve on the water heater itself. There is a hose connected to it that may drain directly into a lower part of the bielge that you can not see (under your cabin floor). This is exactly what was happening to mine. You be hearing your bilge pump run peridically though. Its an easy fix. The valves are standard and can be found in your hardware store. The the old one with you for correct size.
 
I had my HWH pressure relief valave go bad last year when the water heater was on. As the temp increased the valve leak alot more. Replace valve and problem was fixed.

Stuart
 
Lazy Daze said:
Another option is the pressure valve - the one at (on) the hot water tank, itself (just like on a home hot water tank). There is a black, rubber hose attached to it - it usually empties out the side of the hull. These don't fail too often, but if the lever got bumped (or left) into the open position, it will stay there.
Click to expand...

Mine has no hose and will drain right into the bilge, but since it's under pressure anyway, I could probably route it up to the cockpit drain that's directly above my WH...? For those of you with this already in-place, is it tied into an existing cockpit drain? If so, is there a check valve or is it just positioned high on a loop to avoid drain water flowing down to the WH? Maybe something for my to-do list.
 
Hi guys:
I want to take advantage of this forum because I have a problem with my Fresh water tank. (1997 Sundancer 40).
I fill the tank and wait until the water start coming out of the overflow. After 1/2 an hour the rear state room floor was flooded. I emptied the tank and investigated inside and remove everything so I could see the tank. Filled the tank again and when it was almost full it started to grow like a ballon and water started to come out of the floor. As soon as I release the pressur the water will stop coming out (I do not know from where)
Right know the tank is almost full and no water coming out.
Any information will be highly appreciated.
 
"Grow like a balloon"? You should not have pressure within the fresh water tank. How can you possibly have pressure in the tank when it pours out of the vent when the tank is filled?
 
Likely, the vent line is not run properly and either has a low spot in it (water has accumulated there) or the vent itself is clogged.

You may have a crack in the tank and it's small enough (or high enough) that water only comes out when the tank is under pressure or filled high enough.
 
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giangi said:
Hi guys:
I want to take advantage of this forum because I have a problem with my Fresh water tank. (1997 Sundancer 40).
I fill the tank and wait until the water start coming out of the overflow. After 1/2 an hour the rear state room floor was flooded. I emptied the tank and investigated inside and remove everything so I could see the tank. Filled the tank again and when it was almost full it started to grow like a ballon and water started to come out of the floor. As soon as I release the pressur the water will stop coming out (I do not know from where)
Right know the tank is almost full and no water coming out.
Any information will be highly appreciated.
Click to expand...

Keep tearing things apart until you find the answer! (because I want to know!!!)

All early 400DA's do this. (my tank doesn't bulge, but I've vacuumed up a lot of water over the years)

I can tell you:

- it's not the tank itself (as you know, the tank will stay completely full for months if you want it to, you just can't over-fill)
- It's not the connection at the overfill through-hull. I've had the fridge out looking for signs of moisture on the vent/overflow line, and that area was completely dry.

I keep promising to find the answer once and for all, but all these years later, I just make sure to never over fill. (it will also leak if you fill very quickly)
 
RC: I'm not sure exactly how your HWH is positioned, but you could just run a rubber hose further into the bilge so if it does open, I doesn't spray anything else.

Tying into your cockpit drain... I'm trying to think of a reason why you can't do this and I can not. If you run the hose high enough, above your tie-in point, you shouldn't have any problem with back flow. However, this will be one more area that will need to be winterized. But that can be accomplished by simply opening the valve (while the tank is draining) and just making sure you "work" any low spots in the hose back to the valve.

Or, just install a small through hull (above water line) on the side of the hull if that would be easier. Again, I'm not sure of your layout to say which would be better.
 
Thank you very much everybody for your reply.
I am going to keep an eye on it. Now two things I am sure: I was filling the tank too quickly and waiting too long for the water to overflow.
I will keep you posted.
 
It was the hwp valve.. Thank you all for the help... This site is great and can save you alot of money......
 
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