Holding Tank issue

Hi all,



I would appreciate you thoughts and advice on the following:



The holding tank of my (fresh water) head is filling up with water despite the fact that my fresh water pump and heads have been turned off. I suspect the water is getting in through the overboard discharge seacock. The holding tank is below that waterline.



Based on what little I know, the only solution would be to replace the seacock. I'm thinking of putting cap on the seacock and the waste hose to temorarily seal it off until my next haul out - when I can replace the seacock.



Notes:
- The seacock is not frozen, shows no signs of external damage and appears to be fully closed (based on the handle position against the stop).
- The tank contents look like clear water

- The tank does not appear to be distended, but the tank hold down straps have failed (screws pulled from wood anchor points) indicating that the tank is under pressure (?). I checked the vent and it doesn't seem to be clogged. The tank does not appear to be distended. This failure occurred within that last few days.
- This is my first post, though I've been following the forum for a couple of years.



Thanks in advance,

Tom

The seacock is not typically incorporated with a check valve, so I doubt that is your issue. If you can discharge overboard, you should have a mascerator after the tank and then into a vented loop. The vented loop is what keeps water from flowing backwards. Find it at the top of the loop and unscrew, inspect and clean the little valve which will be a small piece of rubber. That should get it working again. In the meanwhile, close the seacock so you lessen the risk of sinking.

Welcome aboard. I agree that it may be the vented loop that is malfunctioning. Peggie will probably chime in and what she says is where I would start.

So is the discharge seacock for your holding tank below the waterline? Unfortunate if it is. If it is, then I would agree with Ghost and Comodave that it sounds like a siphon issue as well as a bad seacock. I would check the vented loop to make sure that you actually have one, and that it is functioning. If you can find it and ensure it is working, and your tank no longer fills up, then you can look to the seacock at your next haulout.


However, if checking, cleaning the vented loop doesn't solve the problem, then I would haul out right now. Your boat is trying to sink and the only thing keeping it from doing so is the integrity of your holding tank and its fittings.

I don't understand why the tank would be under pressure. Even If the discharge hose is under water the tank would fill but shouldn't be under enough pressure to pop screws out. And if the vent is functioning it should never be under pressure. I would think water would have to be pumped in to the tank and the vent totally clogged to buildup pressure. I would remove the deck pump out cap to see if there is pressure.

For sure- your fresh water tank is not losing any water during the same time?

Gmarr said:

For sure- your fresh water tank is not losing any water during the same time?

Click to expand...

That's my question as well.

Taste the water in the tank to see if it’s salty. Sorry,I couldn’t help myself.
Welcome aboard.

HopCar said:

Taste the water in the tank to see if it’s salty. Sorry,I couldn’t help myself.
Welcome aboard.

Click to expand...

:lol:

The holding tank of my (fresh water) head is filling up with water despite the fact that my fresh water pump and heads have been turned off. I suspect the water is getting in through the overboard discharge seacock. The holding tank is below that waterline. Based on what little I know, the only solution would be to replace the seacock.

Nope...that won't solve the problem unless you're keeping the seacock closed at all times except while dumping the tank.

If it's sea water that's filling even when the seacock is closed, replace the seacock and also install a vented loop in the tank discharge line that's at least 6-8" above waterline and continue to keep the thru-hull closed except when dumping the tank.

However, if it's NOt sea water, there's a good chance that the solenoid valve in the toilet intake line has failed, allowing water to to flow into the bowl and from the bowl into the tank. The cure: replace the solenoid valve. But also install the vented loop in the tank overboard discharge line and keep the thru-hull closed except while dumping the tank.

--Peggie

All,
Thanks for your replies. Additional information based on comments and advice:


- the system is not equipped with a vented loop
- seacock/discharge is below the water line
- I keep the seacock closed at all times unless actively dumping
- I don't think it's filling with potable water because I carry 100 gallons of water and would see a reduction in the amount of water on board if it flowed into the 40 gallon waste tank which should be almost empty.



My plan is to get it pumped out today and install a Sealand ball valve in the discharge line and then see if I fit a vented loop in somehow. if that cures the problem, I'll have the seacock replaced at next haulout. If not, I'll replace the solenoid valve as Peggy suggests.



Thanks again for your comments and advice.



Tom

I'm not sure I'd be too quick to add another valve. One (the thru hull) is sufficient, two complicates things. You can troubleshoot the problem without the addition of the valve. Do the vented loop, for sure. If the tank is below WL, it's a must. Lacking that could sink the boat. It relies on no one to insure it's in the correct position, it can't be inadvertently left open, it can't leak through. Physics is pretty consistent.