Water tanks not emptying simultaneously

Well, this is odd. We have two 150 gallon each water tanks on our Manatee. The port tank has decided it isn't giving up its water. Usually both tanks drain equally. Knew something was up with our list. It seemed to self correct after a section of our cruise stopped but it is now back. I'm thinking bad check valve? Crud in the line?
Do we even need a check valve in the system?
I'm tempted to try ER repair by cutting out the suspect copper line and replacing with hose till cruise back to Chesapeake is complete.
Tilt fully yours
Bob
KASSIE
KK 3693

Did you check to see if your vent was clogged? You could try opening the fill cap and leaving it off to see if the tank empties. If so, it will be a vent issue.

You seem to be on the right track in your thinking. Where in the system is the check valve ? You would not typically need one on the outlet side of the water tanks. I would assume that you have a tee somewhere joining the outlet lines prior to the pump. Try dismantle at tee and give it a shot of air up the suspect line.

I would shoot some water up the supply line, water jet is more power and weight behind it than air pressure.

I you have a wet vac, try sucking on the line first.

Yes, water does weigh more than air. The "force" is measured in Pounds of pressure per square inch of surface. You may be able to supply 80 to 90 psi of water pressure to the lines via a hose if you have a shore supply of water but don't try it off of your internal water pump because your suction (supply line) will be disconnected. The "weight " of the water has little to do with it. Furthermore if I had to clean up a mess of something I would rather clean up a lot of spilled air than spilled water.

ulysses said:

Yes, water does weigh more than air. The "force" is measured in Pounds of pressure per square inch of surface. You may be able to supply 80 to 90 psi of water pressure to the lines via a hose if you have a shore supply of water but don't try it off of your internal water pump because your suction (supply line) will be disconnected. The "weight " of the water has little to do with it. Furthermore if I had to clean up a mess of something I would rather clean up a lot of spilled air than spilled water.

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ulysses said:

Yes, water does weigh more than air. The "force" is measured in Pounds of pressure per square inch of surface. You may be able to supply 80 to 90 psi of water pressure to the lines via a hose if you have a shore supply of water but don't try it off of your internal water pump because your suction (supply line) will be disconnected. The "weight " of the water has little to do with it. Furthermore if I had to clean up a mess of something I would rather clean up a lot of spilled air than spilled water.

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I assume the tank is in the bilge, so what if it gets wetter.
Water flow has more power since it has greater mass, regardless of the psi.
I have backflushed plenty of lines with water, it is effective.

There looks to be a t with cap on the one outlet side of port tank, a few feet later port and starboard are joined. Maybe it's not a check valve but instead a clean out? But it's only on the one tank. Took cap off and there was like a crown of crud which disintegrated in my fingers. Very difficult access, so when I go back in again I want to be able to fix and not lose more blood.
I agree, I see no reason for a check valve on output side.
Thanks for all the responses.
Bob

A clogged vent is a good possibility. There should be a valve at the outlet of each tank. Maybe the valve got partially closed somehow.


It's unlikely that you have "crud" in the lines, assuming that you are careful what you put in the tank. This is your drinking and cooking water.


I wouldn't expect to find a check valve, but if there is one, it could be stuck and causing the problem.

I'm leaving the fill caps off for now to see what happens over next day or so.

Kaylic said:

I'm leaving the fill caps off for now to see what happens over next day or so.

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Just remember, you will be drinking anything that gets in there.

Why not close the valve from the other side and see if you can draw water from the one that is not emptying. Try with and without the fill cap in place.

Your vent may have a screen. It's not really needed and it's an opportunity for a clog or insect nest. Checking it is nothing more than looking at it. Pretty simple.

Greetings,
Mr. K. Pending your solution to not being able to pass water...IF there is a blockage of something in the water line, I would be much more inclined to suck on the line with, as suggested by Mr. 717, a shop-vac. I wouldn't want to send any "goop???" back into the tank to cause problems in the future.

Wait, what?

Kaylic said:

There looks to be a t with cap on the one outlet side of port tank, a few feet later port and starboard are joined. Maybe it's not a check valve but instead a clean out? But it's only on the one tank. Took cap off and there was like a crown of crud which disintegrated in my fingers. Very difficult access, so when I go back in again I want to be able to fix and not lose more blood.
I agree, I see no reason for a check valve on output side.
Thanks for all the responses.
Bob

Click to expand...

Tee with a cap is probably a drain. Crud and sand are common in PW tanks. Bacterial growth that looks like snot or ectoplasm is common too. Air or water purge would be my first step. Prepare to get wet.

No worries about the blood, chicks dig scars... (old submariner saying)

I had this exact problem in my Marine Trader. One of the tanks drain had a short 1" steel nipple between the stainless steel tank and a brass gate valve. The steel nipple had clogged closed by it's own corrosion.

When I had to take the tank out for other reasons, I was able to remove the nipple and replace with a brass one and apply plumbers tape. Hopefully it will last another 20 years.

Hope yours is as easy a fix.

Many check valves actually look like a tee with a plug on the side. The "plug" actually allows for the cleaning of the swing check inside the tee. You should be able to do away with that entirely. You may have already fixed it somewhat by cleaning out the goop that was created.
As far as exerting a water or air force on the lines Sdowney717 please be aware that weight and mass are two different things. Then you throw in "power". What unit of measurement are you referring to in the power statement ? Power or "force" if you will is actually the mass X the acceleration squared. Think about the acceleration squared number a little in regard to air movement. PSI is PSI air or water a measure of force. Furthermore I always try to eliminate water in my bilges from any source at all times. Just a thing with me I guess.

Thanks for all the replies. Getting dark, alcohol kicking in, doesn't seem like such a big deal right now.???
We have a 45 gallon water bag that we put in our dinghy, fill up at fuel dock and then transfer with small electric pump to water tanks. Guess what, the boat now sits level in the water. If we don't shower, the problem is fixed ... right??

I'll tackle this in am.
Thanks all!!
Bob

Close off the good tank outlet and draw from the bad tank outlet (with the fill cap loose just in case the vent is plugged) If it won't pump, then the tank outlet is plugged somehow by stuck closed check vlv, plugged pipe or whatever.
Sometimes a check valve can be opened by tapping on the valve body.
My vote would be to remove the check valve completely, and leave both tanks aligned in parallel.