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Old 25-07-2021, 16:56   #1
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Holding Tank Monitor problems and suggestions

I am struggling with my holding tank monitor. A bit of background.

I have a Morgan 382. The holding tank is in the keel. This means that the sides are not accessible, so all of the capacitive systems that work that way will not work. The fitting on the top of the tank is a 1-1/4" NPT, so the 5 hole DIN setups will not work, at least not with some difficult work in a difficult to get to place. It is and option, but only if I have tried everything else, and I KNOW that is is a forever fix. Lastly, being at the bottom of the bilge, whatever sensor I put there will be under water.

Years ago I purchased an Electrosense tank monitor. The company no longer exists, but you can still see their offering here: I LOVED this monitor. It worked flawlessly, and during the years I had it, it just worked. Unfortunately, the sensor was built with regular CAT5 wire, molded into the top of the sensor. Underwater in the bilge, it failed. Then I found out Electrosense was no more, and I tossed it to replace with something else. I now regret that, as with some work I could have built a new sensor.

I searched I and low, and there are not many offerings that will fit a 1-1/4 NPT hole. A came across the SCAD monitor, which fits (with and adapter) and is highly regarded as trouble free and accurate. Unfortunately, my experience has been everything but that.

I had problems early because the sensor wires were short, and there was a splice that was sometimes under water. SCAD was helpful enough to custom build me a sensor with longer wires. But the problems persist.

I can calibrate the sensor, which is both smelly and messy, and takes a long time. The only way I know if the tank is full or empty is to remove the sensor and look in it with a flashlight. So, (im sure many have gone through this) pump out the tank, install the sensor, calibrate the empty, remove the sensor, fill the tank, calibrate the full, then pump out again, then fill again to test the meter function, then pump out again.

It works great for a couple tank fills, then gets wonky. Sometimes it will get stuck on a certain level, or it will read full, or empty, or give an error that the 2 calibration points are too close. If I calibrate it again, it will work fine again for a short time.

This is obviously not acceptable to me. I would love something of a similar design to my old electrosense, as it was so simple and other than the flaw of using CAT5 wire for the sensor there wasn't anything to go wrong or out of calibration.

Does anyone have any product ideas? I have considered the 5 hole DIN solution, but the sonic/reflective type sensors have requirements about tank shape, not being too close to a wall, and having needed a flat bottom, so I'm not sure they would work in my keel. So unless there is no other way, I'd like to stick with the NPT fitting.
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Old 25-07-2021, 17:27   #2
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Re: Holding Tank Monitor problems and suggestions

I can’t remember who was selling this for boats. The system is a tiny air pump sending air down a dip tube to the bottom of the tank. Instead of a dip tube you could also simply port externally to the tank or pipe. The principal is a manometer. The tiny air flow keeps the dip tube clear. The pressure in the tube is a direct reflection of the fluid depth. Sensing can be a gauge or electronic sending unit. The units I saw were multi point for several tanks. Naturally, there is a check valve in each sensing leg to prevent tank contents from backing into the line. The master unit cycles through various dip lines. No electronics at the tank.

I used to see these advertised in the sail and marine magazines. Google hydrostatic tank depth monitor Marine
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Old 25-07-2021, 18:18   #3
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Re: Holding Tank Monitor problems and suggestions

Quote:
Originally Posted by Nicholson58 View Post
I canít remember who was selling this for boats. The system is a tiny air pump sending air down a dip tube to the bottom of the tank. Instead of a dip tube you could also simply port externally to the tank or pipe. The principal is a manometer. The tiny air flow keeps the dip tube clear. The pressure in the tube is a direct reflection of the fluid depth. Sensing can be a gauge or electronic sending unit. The units I saw were multi point for several tanks. Naturally, there is a check valve in each sensing leg to prevent tank contents from backing into the line. The master unit cycles through various dip lines. No electronics at the tank.

I used to see these advertised in the sail and marine magazines. Google hydrostatic tank depth monitor Marine


Headhunter tank sentry perhaps?

https://www.headhunterinc.com/product/tank-sentry-2/
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Old 25-07-2021, 19:16   #4
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Re: Holding Tank Monitor problems and suggestions

Souped up version of the simple one I saw. There may be others similar
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Old 25-07-2021, 20:36   #5
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Re: Holding Tank Monitor problems and suggestions

You can still use a SCAD system Scad Tank Monitors They have a sensor that's actually made for use in metal tanks, but no reason why it can't be used in any tank that can't use an external sensor. The sensor goes inside the tank...it's in a PVC tube that prevents tank contents from coming in contact with it so it can never get clogged or corroded.

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Old 26-07-2021, 04:30   #6
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Re: Holding Tank Monitor problems and suggestions

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Originally Posted by Sailmonkey View Post
Holy hell, that is $1600 !!!!!

It looks like a great system, and looks pretty simple. I don't understand the price. It is about 10x what I can afford.
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Old 26-07-2021, 04:33   #7
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Re: Holding Tank Monitor problems and suggestions

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Originally Posted by peghall View Post
You can still use a SCAD system Scad Tank Monitors They have a sensor that's actually made for use in metal tanks, but no reason why it can't be used in any tank that can't use an external sensor. The sensor goes inside the tank...it's in a PVC tube that prevents tank contents from coming in contact with it so it can never get clogged or corroded.

--Peggie
I have a SCAD monitor, with the internal sensor, as detailed in my post. I have been working with support, and can't get it to work reliably. I don't think a capacitive type sensor will work, because my tank is in the bilge, and the entire sensor is submerged under water.
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Old 26-07-2021, 05:20   #8
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Re: Holding Tank Monitor problems and suggestions

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Originally Posted by wholybee View Post
Holy hell, that is $1600 !!!!!

It looks like a great system, and looks pretty simple. I don't understand the price. It is about 10x what I can afford.
Yup. Thatís exactly what I thought five years ago. I figure the concept is so simple you could make your own with a couple of valves, check valve, air supply and a gauge. You could even blow into the hose. Parts about $100 from McMaster. No electronics. This would let you manually check at will.
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Old 26-07-2021, 05:43   #9
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Re: Holding Tank Monitor problems and suggestions

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Originally Posted by Nicholson58 View Post
Yup. Thatís exactly what I thought five years ago. I figure the concept is so simple you could make your own with a couple of valves, check valve, air supply and a gauge. You could even blow into the hose. Parts about $100 from McMaster. No electronics. This would let you manually check at will.


AhhhhÖÖthatís the tank tender. Equally well priced.

http://tanktender.com/
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Old 26-07-2021, 10:24   #10
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Re: Holding Tank Monitor problems and suggestions

Quote:
Originally Posted by Nicholson58 View Post
I canít remember who was selling this for boats. The system is a tiny air pump sending air down a dip tube to the bottom of the tank. Instead of a dip tube you could also simply port externally to the tank or pipe. The principal is a manometer. The tiny air flow keeps the dip tube clear. The pressure in the tube is a direct reflection of the fluid depth. Sensing can be a gauge or electronic sending unit. The units I saw were multi point for several tanks. Naturally, there is a check valve in each sensing leg to prevent tank contents from backing into the line. The master unit cycles through various dip lines. No electronics at the tank.

I used to see these advertised in the sail and marine magazines. Google hydrostatic tank depth monitor Marine
It's called Tank Tender by Hart systems. I monitor 4 tanks with mine 2 Diesel, 1 Fresh water and one waste. Very simple, no electronics. Original equipment on this boat that is 40 years old.
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Old 26-07-2021, 10:53   #11
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Re: Holding Tank Monitor problems and suggestions

I second the suggestion to look into the Tank Tender system. It has a valving system that prevents cross contamination. It's simple to install and simple to use. HART provides great support too. I've had mine for 23 years. JMHO
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Old 26-07-2021, 11:03   #12
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Re: Holding Tank Monitor problems and suggestions

There are plenty of ultrasonic systems out there if you look around. This one on Amazon, for example @ £50 - https://www.amazon.co.uk/Homyl-Ultra.../dp/B07SLTX7XQ
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Old 26-07-2021, 11:57   #13
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Re: Holding Tank Monitor problems and suggestions

Quote:
Originally Posted by Nicholson58 View Post
I canít remember who was selling this for boats. The system is a tiny air pump sending air down a dip tube to the bottom of the tank. Instead of a dip tube you could also simply port externally to the tank or pipe. The principal is a manometer. The tiny air flow keeps the dip tube clear. The pressure in the tube is a direct reflection of the fluid depth. Sensing can be a gauge or electronic sending unit. The units I saw were multi point for several tanks. Naturally, there is a check valve in each sensing leg to prevent tank contents from backing into the line. The master unit cycles through various dip lines. No electronics at the tank.

I used to see these advertised in the sail and marine magazines. Google hydrostatic tank depth monitor Marine
These were Hart systems I think. You could even multiplex upto 4 tanks. No electricity needed. Its based on level measurement I learned about when doing instrumentation for waste water treatment plants.

I built my own using a weighted pipe fed through the top of the tank through a gland. the pipe had a squeeze bulb from a blood pressure machine at the top end and a T just before the T. on the leg of the T is a pressure gauge. My tank is 15" high so I found a pressure gauge with 15" water full scale. Was a bit tough to find. A manometer would also work.
You pump the bulb until the needle gets to a stable maximum. At this point air is exiting the bottom end of the tube and the pressure equals the height of the liquid. You look at the gauge to see the liquid height. Taking readings also keeps the tube clear. If you cannot find a bulb, blow (don't suck) into the tube.
For continuous reading, get a bubbler and control the flow so that bubbles are just rising. Has the additional benefit of aerating the tank which promotes aerobic decomposition rather than the smelly anaerobic decomposition.
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Old 26-07-2021, 12:18   #14
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Re: Holding Tank Monitor problems and suggestions

I have installed the Hart Tank Tender system on my last two boats. Expensive, but strongly recommended. It is accurate, durable and reliable.

Quote:
Originally Posted by Jack C View Post
These were Hart systems I think. You could even multiplex upto 4 tanks. No electricity needed. Its based on level measurement I learned about when doing instrumentation for waste water treatment plants.
On our boat the single Tank Tender system monitors the level in 8 tanks, but this can be expanded if required.
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Old 26-07-2021, 13:15   #15
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Re: Holding Tank Monitor problems and suggestions

Quote:
Originally Posted by wholybee View Post
I am struggling with my holding tank monitor. A bit of background.

I have a Morgan 382. The holding tank is in the keel. This means that the sides are not accessible, so all of the capacitive systems that work that way will not work. The fitting on the top of the tank is a 1-1/4" NPT, so the 5 hole DIN setups will not work, at least not with some difficult work in a difficult to get to place. It is and option, but only if I have tried everything else, and I KNOW that is is a forever fix. Lastly, being at the bottom of the bilge, whatever sensor I put there will be under water.

Years ago I purchased an Electrosense tank monitor. The company no longer exists, but you can still see their offering here: I LOVED this monitor. It worked flawlessly, and during the years I had it, it just worked. Unfortunately, the sensor was built with regular CAT5 wire, molded into the top of the sensor. Underwater in the bilge, it failed. Then I found out Electrosense was no more, and I tossed it to replace with something else. I now regret that, as with some work I could have built a new sensor.

I searched I and low, and there are not many offerings that will fit a 1-1/4 NPT hole. A came across the SCAD monitor, which fits (with and adapter) and is highly regarded as trouble free and accurate. Unfortunately, my experience has been everything but that.

I had problems early because the sensor wires were short, and there was a splice that was sometimes under water. SCAD was helpful enough to custom build me a sensor with longer wires. But the problems persist.

I can calibrate the sensor, which is both smelly and messy, and takes a long time. The only way I know if the tank is full or empty is to remove the sensor and look in it with a flashlight. So, (im sure many have gone through this) pump out the tank, install the sensor, calibrate the empty, remove the sensor, fill the tank, calibrate the full, then pump out again, then fill again to test the meter function, then pump out again.

It works great for a couple tank fills, then gets wonky. Sometimes it will get stuck on a certain level, or it will read full, or empty, or give an error that the 2 calibration points are too close. If I calibrate it again, it will work fine again for a short time.

This is obviously not acceptable to me. I would love something of a similar design to my old electrosense, as it was so simple and other than the flaw of using CAT5 wire for the sensor there wasn't anything to go wrong or out of calibration.

Does anyone have any product ideas? I have considered the 5 hole DIN solution, but the sonic/reflective type sensors have requirements about tank shape, not being too close to a wall, and having needed a flat bottom, so I'm not sure they would work in my keel. So unless there is no other way, I'd like to stick with the NPT fitting.
I tried to wade thru the thread so I apologize if someone else posted this already. One of my marina neighbors sent me the link to this company - Their holding tank, fuel and water tank sensors are what he just installed and he said he couldn't be happier.

https://kus-usa.com/application-solutions/marine/

I'm about to install the same set on my boat.
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