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Holding Tank Level

  • Thread starter Thread starter jmagel
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jmagel

jmagel

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  1. OWNER - I own a Hatteras Yacht
Hatteras Model
48' MOTOR YACHT-Series II (1990 - 1995)
Moved to a new marina in Brooklyn for the rest of the season and local pompout boat got 0 out of our holding tank after many days of use. It's been pumping out OK in our old location. Pretty sure our tank sensor is shot (never seen the 3/4 light in 4 years of ownership) so wondering what's the easiest method of checking the tank level manually? which fitting is "easiest" to remove to get a dipstick in?

Thanks!
 
Unscrew the sender and stick a stick into the hole. Are you sure your suction tube has not fallen off from decay.
 
Not sure about anything yet. Thanks for the help - going to check it out tonight or tomorrow.
 
Inspected the entire run of hose and all looks in good shape. Also tried to unscrew the sender, but it didn't budge -- even with some hammering. Didn't want to hit too hard though. Is the sender supposed to unscrew? Mine has a rigid metal pipe connected to the top. Even if I could get it to move, it doesn't look like it would unscrew. Attached a pic...

Also - if I wanted to check the tube for a block, what's the best tool? Standard snake or is that too rough?

Thanks!
 

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If your tank/setup is original, the sender is located at the other end of that tube from the tank. It is a circular unit, about the size of a thick hockey puck. The hockey puck will have a short piece of rubber hose attaching it to the copper tube. To test the system, you can attach a new piece of hose to the sensor, have someone watch the 3/4 full light in the head compartment, and blow lightly into the new rubber hose which is attached to the sensor - like blowing up a balloon but VERY lightly. The light should illuminate - be sure the bulb is OK first.

If the bulb illuminate, that shows that the sensor/circuit are ok. NOW you have to determine if the tube in the tank is ok. The only way to do that that I know of is to just stick a water hose in the pumpout fitting and fill the tank. If water starts coming out the vent before the light goes on, the tube in the tank is perforated and has to be replaced.

Obviously you could install a real tank-level system and that's certainly a good thing. But I have found the 3/4 full OEM system to work just fine for our use. I had to install a new 3/4 full sensor tube in our forward tank.

The OEM system is nothing more than a piece of tubing - can't recall the diameter - seems like it might be 1" but I could be wrong - with an adapter on top to accept the fitting for the 1/4" tube/hose. As the tank fills, the air pressure increases in the tube which activates the sensor/light. The length of the tube determines the point at which the light illuminates. IF the tube is too long, it will illuminate too early; If too short, the tank will be nearly full.
 
Last edited:
If the pressure switch works, its likely that both the sender tube and the suction tube for the pump out are corroded off. Mine was. The sensor tube is 4 - 5" long inside the tank and the suction tube should go to the bottom of the tank cut at about 45 degrees at the bottom. Sam's had sensor tubes when I needed one. Best to fab a suction tube out of PVC so it won't corrode. You will need to remove both and inspect. Remove as much of the sealant around the fitting as possible and spray with PB blaster and let sit overnight. I wouldn't use a hammer for fear of cracking the fiberglass tank.
 
jmagel said:
Inspected the entire run of hose and all looks in good shape. Also tried to unscrew the sender, but it didn't budge -- even with some hammering. Didn't want to hit too hard though. Is the sender supposed to unscrew? Mine has a rigid metal pipe connected to the top. Even if I could get it to move, it doesn't look like it would unscrew. Attached a pic...

Also - if I wanted to check the tube for a block, what's the best tool? Standard snake or is that too rough?

Thanks!
Click to expand...

The sending unit, if it's like mine is the one on the bottom of this photo. It's the one with the square head. It has a copper tube coming out of it going to a micro switch. Take a torch to it and warm up the threads. It's all brass so it won't take long. Give me your feed back once you try that.
 
MikeP said:
If your tank/setup is original, the sender is located at the other end of that tube from the tank. It is a circular unit, about the size of a thick hockey puck. The hockey puck will have a short piece of rubber hose attaching it to the copper tube. To test the system, you can attach a new piece of hose to the sensor, have someone watch the 3/4 full light in the head compartment, and blow lightly into the new rubber hose which is attached to the sensor - like blowing up a balloon but VERY lightly. The light should illuminate - be sure the bulb is OK first.

If the bulb illuminate, that shows that the sensor/circuit are ok. NOW you have to determine if the tube in the tank is ok. The only way to do that that I know of is to just stick a water hose in the pumpout fitting and fill the tank. If water starts coming out the vent before the light goes on, the tube in the tank is perforated and has to be replaced.

Obviously you could install a real tank-level system and that's certainly a good thing. But I have found the 3/4 full OEM system to work just fine for our use. I had to install a new 3/4 full sensor tube in our forward tank.

The OEM system is nothing more than a piece of tubing - can't recall the diameter - seems like it might be 1" but I could be wrong - with an adapter on top to accept the fitting for the 1/4" tube/hose. As the tank fills, the air pressure increases in the tube which activates the sensor/light. The length of the tube determines the point at which the light illuminates. IF the tube is too long, it will illuminate too early; If too short, the tank will be nearly full.
Click to expand...

Well written Mike. I just helped a friend completely re-do his 43. I wish I would have seen this post before we started.
 
Thanks for all the info! I will def check out the sensor again (think I did this a few years back with no luck), but I don't have a torch (or the confidence) to safely release that fitting. Prob going to bring in some help, but I'll report back.

I would love an accurate reading on the tank, though. Anyone use tank tender or recommend another product?
 
Jon, this is so easy. I can talk you through it on the phone if you want. If so send me your cell number on a PM and a time I should call. The torch is cheap.
 
Installed a Hart Tank Tender years ago. Accurate to within a gallon or two. Only gauge I have ever found that lasts in a holding tank.
 
SKYCHENEY said:
Installed a Hart Tank Tender years ago. Accurate to within a gallon or two. Only gauge I have ever found that lasts in a holding tank.
Click to expand...

Sky,

Have you had any problems with the tank penetration fitting in the holding tank? In my case, the TPF was corroding and dropping the dip tube in a fairly short time. I devised a robust one out of silicone bronze which has lasted several years now. Otherwise the Hart Tank Tender is a great gauge.

Bobk
 
SEVEN said:
Jon, this is so easy. I can talk you through it on the phone if you want. If so send me your cell number on a PM and a time I should call. The torch is cheap.
Click to expand...

Very generous offer! Thank you. I might take you up on that when I get into trouble shooting. Going to run all the tests to see if the system is working first.

...And good news... Brought boat to pump out station and tank emptied with no problem. The suction from the pump out boat must not have been strong enough.
 
Lucky
 
Glad to hear you were able to get everything out. I have run into similar issues in the past. Fortunately, we are on a two week auto-pump out in our marina. Normally, they are pretty good. For sanity sake and I don't trust the "3/4 full" light, I go old school and simply knock on the side of the tank to check the level - simple but effective.
 
bobk said:
Sky,

Have you had any problems with the tank penetration fitting in the holding tank? In my case, the TPF was corroding and dropping the dip tube in a fairly short time. I devised a robust one out of silicone bronze which has lasted several years now. Otherwise the Hart Tank Tender is a great gauge.

Bobk
Click to expand...

I have not had any problems.
 
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