Tank Monitor Installations

Jan 11, 2014
7,824
Sabre 362 113 Fair Haven, NY
The time has come to add tank monitors to the holding tank and probably 2 water tanks.

As I look at the various technologies most of them require a sending unit inside the tank which means installing a new hole in the top of the tank. Due to the locations of the tanks an external sensor, like the SCAD sensors are only viable on 1 of three tanks and that tank is the easiest one to visually inspect.

The tanks are all polyethylene. The tank sensors I've looked at Maretron, Dometic, and others all have screws to hold the top of the sensor down. I'm skeptical of this arrangement especially on the holding tank.

What have others done? Suggestions? Are my fears of a leaking holding tank over blown?

Thanks.
 
Apr 1, 2004
110
Catalina 34 Herring Bay Chesapeake, MD
The time has come to add tank monitors to the holding tank and probably 2 water tanks.

As I look at the various technologies most of them require a sending unit inside the tank which means installing a new hole in the top of the tank. Due to the locations of the tanks an external sensor, like the SCAD sensors are only viable on 1 of three tanks and that tank is the easiest one to visually inspect.

The tanks are all polyethylene. The tank sensors I've looked at Maretron, Dometic, and others all have screws to hold the top of the sensor down. I'm skeptical of this arrangement especially on the holding tank.

What have others done? Suggestions? Are my fears of a leaking holding tank over blown?

Thanks.
Try checking Scad Technologies scadtech.com
These are all outside tank level indicators.

Peggy Hall may also have suggestions about external indicators.

Good luck,

Steve
 
Jan 4, 2006
3,899
Hunter 310 West Vancouver, B.C.
Use an external sensor for the holding tank so any otherwise internal floats don't get crapped up :poop:.

Use a WEMA float sensor on water tanks as I believe all external sensors require a certain level of conductivity to work. And yes, you will require an access hole but it's only clean water if it should decide to leak. Is there any chance of installing an "official looking" deck plate over the tanks which you have great difficulty accessing ? Don't know what you will be penetrating to access the top of the tank.

1609720800733.png
 
Dec 2, 1997
8,120
- - LIttle Rock
If you look under "features" on the SCAD site Scad Tank Monitors you'll see that they offer an internal sensor "for metal tanks"...but it can be used in tanks of any material. The sensor is encased in a pvc tube, so it never comes in contact with tank contents...offering all the advantages of an external sensor. You might want to give 'em a call to discuss.

--Peggie
 
Jul 7, 2004
8,004
Hunter 30T Cheney, KS
If you look under "features" on the SCAD site Scad Tank Monitors you'll see that they offer an internal sensor "for metal tanks"...but it can be used in tanks of any material. The sensor is encased in a pvc tube, so it never comes in contact with tank contents...offering all the advantages of an external sensor. You might want to give 'em a call to discuss.

--Peggie
That's what I use in my metal holding tank. Works fine. It should work in the plastic tanks just as well
 
Oct 2, 2008
3,584
Pearson/ 530 Strafford, NH
We’ve had Headhunter tank monitoring for our holding tanks and they have performed well. I’ve also been able to contact them for support. I have a different monitor for fuel and fresh water, I use my own calculations for keeping track of those.
 
Apr 8, 2011
465
Hunter 36 Deale, MD
I'll throw out another alternative - one that I use for my plastic holding tank: Gobius Pro. I just want to know when my holding tank is 2/3 of the way full so I can pump out before it gets critical. The factory holding tank sensor on my 2009 Hunter 36 is non-functioning and access to replace it is difficult. So I just repurposed the existing power leads for the Gobius Pro sensor, placed it 2/3 of the way up the tank, and at a glance I can tell when it reaches 2/3 full by a light turning from green to red in the cabin. Takes very little power. I typically pump out pretty frequently, but on a longer trip of several days on the hook it is useful for fair warning. Installation is stupid easy, and NO pulling anything out of your tank - its an external ultrasonic sensor. You can install multiple sensors to gauge a finer sense of tank level, but for me one is enough.

Not for every use case, but I definitely find it useful and it was very easy to install. www.gobius.se/en/
 
Jul 12, 2011
984
Catalina 36 1771 Ft Pierce, Florida
I installed a SCAD external sensor to my holding tank (bought it directly from Firriello, who invented and made them) and it is still working great after three years with no maintenance. Basically, you stick on two metal strips a measured distance apart on the outside of your plastic tank, whatever shape, and it tells you the percent fill in 1/4 increments. Worst part of the installation was running the wires and cutting the mounting hole for the control unit. Only reason to cut into a tank would be for metal tanks, in my opinion.
 
Dec 2, 1997
8,120
- - LIttle Rock
That's what I use in my metal holding tank...
Uh oh.......Metal--neither alumimum nor steel--is recommended for waste holding because urine is so corrosive that it'll even eat through 316 stainless. The first leak almost always occurs at a weld--a seam or a fitting, usually within 2-5 years...and the first leak is always ONLY the FIRST leak...urine is gradually turning the bottom of the tank into a colander.

This isn't cause for panic...your first clue will be a bit of odor in the location of the tank...find the leak and patch it with JB Weld. That's the best time to start planning to replace the tank with a top quality plastic tank.

--Peggie
 
Dec 2, 1997
8,120
- - LIttle Rock
I installed a SCAD external sensor to my holding tank (bought it directly from Firriello, who invented and made them) and it is still working great after three years with no maintenance.
SCAD did sell the Feriello Profile tank monitors under the SCAD brand name for several years, but had to discontinue that when Dennis Feriello died last year and his mfr'g supplier (New Providence Marine) also folded. SCAD now sells their own design that continues to be the top rated water and waste tank monitors, but still offers tech support and replacement parts for the Profile monitors...you'll find that as "Legacy montiors" on the SCAD site.

--Peggie
 
Jul 7, 2004
8,004
Hunter 30T Cheney, KS
Uh oh.......Metal--neither alumimum nor steel--is recommended for waste holding because urine is so corrosive that it'll even eat through 316 stainless. The first leak almost always occurs at a weld--a seam or a fitting, usually within 2-5 years...and the first leak is always ONLY the FIRST leak...urine is gradually turning the bottom of the tank into a colander.

This isn't cause for panic...your first clue will be a bit of odor in the location of the tank...find the leak and patch it with JB Weld. That's the best time to start planning to replace the tank with a top quality plastic tank.

--Peggie
Thanks for the reminder Peggy. I know from your older posts that metal tanks are risky. I examined mine (on the outside) very carefully before I chose to go this route. It still looks good after 30 years. We add a water treatment into it often. That might be why.
 
Dec 2, 1997
8,120
- - LIttle Rock
Dennis and I were good friends for more than 20 years. Not only was he one of the nicest people I've ever known, but he made a top quality product and was the only person I've ever known who'd even answer the phone on a Sunday to help someone with an installation issue. I really miss him!

--Peggie
 
Jan 11, 2014
7,824
Sabre 362 113 Fair Haven, NY
Thanks for the suggestions. The tops of the tanks are accessible, it is the sides of the tank that are not without major deconstruction of the boat. There is one tank that is accessible, because it leaked and I had to pull to get it repaired. If I go with Scad, it will get the external sensor.

The 2 I've been looking at are the SCAD metal tank sensor and a Maretron N2K sensor with a focus tube. Both of these require cutting a hole in to the top of the tank, inserting a tube and screwing it down with a gasket. Part of my concern is whether the screws will bite into the polyethylene sufficiently to get a good seal. For the fresh water tank this means losing a little water, for the black water tank, it will more than water. :( The location of the holding tank also complicates the installation as it is up against the port side hull, thus when heeling even with a half full tank liquid can potentially reach the sensor hole.

I'll give SCAD a call to see what they say.

Thanks again.
 
Jan 11, 2014
7,824
Sabre 362 113 Fair Haven, NY
Pics of your situation might help them advise.
Found one photo that sort of shows the holding tank. It is the white tank in the upper left corner, under the wire ties. There is no clearance between the partial bulkhead and the tank and that bulkhead is tabbed into the hull. The tank extends below the floor the HW tank is sitting on.
The blue area behind the water tank is the hull.

I think Sabre started with a fuel tank and a holding tank and built a boat around them.

IMG_1309.jpeg
 
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Likes: marchem
Jul 12, 2011
984
Catalina 36 1771 Ft Pierce, Florida
At least you can get to your hot water heater! That comment about building the boat around something really hurts us Catalina owners in regards to hot water heaters!

Personally, I'd rather cut wood and fiberglass than break the seal of a holding tank, but perhaps your sense of smell is not as acute as mine. @Peggie used to reference a cool seal that works great on poly tanks, and perhaps it can be adapted to take a sensor. No screws needed as it was compression based, like a motorboat plug.
 
Jan 11, 2014
7,824
Sabre 362 113 Fair Haven, NY
Personally, I'd rather cut wood and fiberglass than break the seal of a holding tank, but perhaps your sense of smell is not as acute as mine. @Peggie used to reference a cool seal that works great on poly tanks, and perhaps it can be adapted to take a sensor. No screws needed as it was compression based, like a motorboat plug.
I've used a uniseal on a holding tank with no problem and no odor. They do work. I think calling SCAD is probably the best bet now.

As for building boats....

 
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Likes: Parsons
May 6, 2010
464
1984 Oday 39 79 Milwaukee
I am contemplating an cleanout access in my fuel tank and have been looking at these access plates: https://diesel-fuels.com/fuel-tank-access/ If you watch the short video in the left margin, it demonstrates the way the system seals. I would think you could fabricate a backing plate similar to what these use to go on the inside of the tank to insure you have a positive seal.
 
Jan 11, 2014
7,824
Sabre 362 113 Fair Haven, NY
I am contemplating an cleanout access in my fuel tank and have been looking at these access plates: https://diesel-fuels.com/fuel-tank-access/ If you watch the short video in the left margin, it demonstrates the way the system seals. I would think you could fabricate a backing plate similar to what these use to go on the inside of the tank to insure you have a positive seal.
Thanks. This looks very interesting. I could install this access port and install the tank monitor in the access plate. Expensive, however it would be secure. My fuel tank does not have an inspection port, so I might add one there.