Water tank over flowing when tap (to pump) on/open

R

Ruthine

.
Nov 6, 2025
26
Hunter Hunter Legend 40.5 Alcadesia Marina, La Linea
dLj said:
Your internal water tanks should be completely sealed - depending upon how they are set up, they should have a vent to allow the air to escape when filling - that vent also works as an "overflow" but it's real function is to allow the air to come out as you fill your tanks and allow air to come in when using your tanks. Depending upon your design setup you may have more than one vent.

While it is a good idea to draw from one tank at a time, it shouldn't be necessary - your tanks and all internal connections should be completely water tight such that only the vent is allowed to breath. In order to know how best to run your water tanks, you need to know how your vents are setup.

I would guess your vent, or vents, are clogged.

dj
Click to expand
Thanks DJ, we are gradually getting there. The tanks seem fine now. We have closed off three of the tanks (after emptying them a bit) and going forward will use one tank at a time. We will need to clean out the bilge as it is clogged with loads of crap and muck. It wasn’t pumping and we had to empty the bilge manually as a consequence. So slowly getting there. We both feel loads calmer today. Being new boat owners is a bit like being new parents.
 
dLj

dLj

.
Mar 23, 2017
4,728
Belliure 41 Back in the Chesapeake
Ruthine said:
Thanks DJ, we are gradually getting there. The tanks seem fine now. We have closed off three of the tanks (after emptying them a bit) and going forward will use one tank at a time. We will need to clean out the bilge as it is clogged with loads of crap and muck. It wasn’t pumping and we had to empty the bilge manually as a consequence. So slowly getting there. We both feel loads calmer today. Being new boat owners is a bit like being new parents.
Click to expand
Hahaha - yes a bit like new parents - however, you don't have to worry about scarring the life of another human - you boat will always forgive you...

dj
 
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smokey73

smokey73

.
Oct 26, 2010
2,171
Hunter 40.5 Beaufort, SC
@Ruthine Your boat info shows you as owning a Hunter legend 42.5 rather than a 40.5. I am assuming you have a 40.5 and all answers are based on that. First thing you need to do is identify the location off all your through hull valves. The following is based on my boat and there may be differences if the PO changed things or they did something different at the Hunter factory.

There are two under the sink cabinet in the forward compartment. The one below the waterline (lowest one) is the is the thru hull for the water intake for the forward head. The one higher is for the sink drain and it is above the water line. I keep both of these close when off the boat.

There are three valves in the bottom of the sink cabinet in the after head. The one on the left (forward) goes to the after head water intake. The middle one goes to the overboard discharge from the mascarator for pumping overboard when legal to do so. This should be kept closed and secured closed (with tie-wrap or lock) when in waters where overboard discharge is prohibited. The one on the right (farthest aft) is the sink drain. All three are below the waterline. I keep all three closed when off the boat.

In the aft cabin under the aft bunk is a large panel that lifts up at the forward edge of the bunk. The thru hull valve for the engine is there. There may be more valves there depending any modification that may have been made like an Air Conditioning Unit, Generator, etc. There is at least the engine thru hull and a sea water filter. I keep the engine thru-hull shut when not in use. I also put the engine key on a ring on the valve handle so I don't start the engine with the valve shut.

I know as a new boat owner it can seem overwhelming but this forum is a wealth of information. Ask away but really try to get to know your boat and all the workings. The 40.5 is a great production boat. It is not a Swan or an Oyster but bang for the buck is pretty high and if you take care of it, it can handle probably more than you can. Ask me how I know?
 
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R

Ruthine

.
Nov 6, 2025
26
Hunter Hunter Legend 40.5 Alcadesia Marina, La Linea
smokey73 said:
@Ruthine Your boat info shows you as owning a Hunter legend 42.5 rather than a 40.5. I am assuming you have a 40.5 and all answers are based on that. First thing you need to do is identify the location off all your through hull valves. The following is based on my boat and there may be differences if the PO changed things or they did something different at the Hunter factory.

There are two under the sink cabinet in the forward compartment. The one below the waterline (lowest one) is the is the thru hull for the water intake for the forward head. The one higher is for the sink drain and it is above the water line. I keep both of these close when off the boat.

There are three valves in the bottom of the sink cabinet in the after head. The one on the left (forward) goes to the after head water intake. The middle one goes to the overboard discharge from the mascarator for pumping overboard when legal to do so. This should be kept closed and secured closed (with tie-wrap or lock) when in waters where overboard discharge is prohibited. The one on the right (farthest aft) is the sink drain. All three are below the waterline. I keep all three closed when off the boat.

In the aft cabin under the aft bunk is a large panel that lifts up at the forward edge of the bunk. The thru hull valve for the engine is there. There may be more valves there depending any modification that may have been made like an Air Conditioning Unit, Generator, etc. There is at least the engine thru hull and a sea water filter. I keep the engine thru-hull shut when not in use. I also put the engine key on a ring on the valve handle so I don't start the engine with the valve shut.

I know as a new boat owner it can seem overwhelming but this forum is a wealth of information. Ask away but really try to get to know your boat and all the workings. The 40.5 is a great production boat. It is not a Swan or an Oyster but bang for the buck is pretty high and if you take care of it, it can handle probably more than you can. Ask me how I know?
Click to expand
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Thank you for this information Smokey73, incredibly helpful! We spent a day opening every bit of storage we could locate. I do feel loads calmer just knowing where all the ‘thru hulls / sea cocks’ are… We do love our Hunter Legend. She’s comfy and roomy. We’ve a lot of work to do tho’ to get her fully ship shape :)
 
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