Holding Tank Modifications using Polyethylene Pipe

More work to my holding tanks! I alluded to some of the benefits of using polyethylene hose for sanitation hose and you can read about it here.

 The first thing I did was remove the input hose and fitting, to the holding tank which was located on the side of the tank. Last year, I had relocated the tank air vent to the top and did a temporary block off, of the old side air vent. You can read about that here. That was located just above and to the side of this fitting seen to the left. I used a Dremel and hacksaw to make the cut of the bronze fitting.

 I prepped the area to get ready to epoxy glue on a cover over the old fittings. Old paint removed and each opening stuffed with toilet paper so that the glue would not full into the tank. The glue is made from two pot epoxy (slow set) with silica powder/binder added until you get the consistency of thick peanut butter.

 To the left is the finished fibreglass plate epoxied to the tank. This year I decided to use some off cuts of fibreglass which are cut out when the boats are removed from the molds. Typically, they are window cutouts and hatch cutouts which are then discarded. You local fibreglass boat builder will have plenty of these to give away.

In preparation for the top fitting, I found the best location; drilled my hole for the polyethylene through hole; and then sanded the area for gluing the fibreglass plate to the tank.

To the left is the finished fitting. You might notice that the black hose it is attached to is polyethylene pipe.
Polyethylene pipe is NOT as flexible as sanitation hose, so you may have to use elbows etc to get it to go where you want to. You can also use boiling water to get a little more curve from the pipe.

To the right you can see the 25mm polyethylene pipe running down and through the wall where it goes to the macerator pump. The bigger 38mm (inch and a half) pipe runs from the bottom of the tank to the "Y" valve and then the polyethylene pipe continues on to the pump out pump. A diaphragm pump with joker valves each end.
Now the outflow is of poor design and should never come from the bottom of the tank, other than a drop down pipe inside the tank, from the top. This is due to the fact that effluent is always in the outflow pipe which leads to permeation  I'm using polyethylene pipe from the bottom of the tank and feel confident, there will be no permeation.

Above you can see I used barrel nuts. This makes presenting pipes up to the fittings real easy. In this case I didn't need to use them, but I had bought them with me, so decided to use them.
To the left you can see the macerator pump with barrel nut fittings at both the inlet and outlet. The outlet has a PVC type which was fitted some time ago. On the other side of the barrel nut, I have a joker valve inside the other half of the PVC barrel nut and then a valve. This is because it is pumping up hill and one day I may need to service.
I have now added a polyethylene barrel nut at the inlet side. Also, but not shown, is a threaded pipe (at the inlet side before the barrel nut), which goes to a valve, before joining up with the 38mm pipe from the toilet bowel. IF the pump needs servicing, I just
turn off the valves at either side of the pump; undo the barrel nuts (usually by hand); disconnect power; and pull the pump out. I have a few "boat towels" to mop up the small amount of fluid that will spill.
And let me say, the area smells so much better already. I might even replace the deck pump out hose ( which goes to the "Y" valve. But my wife says, that is just looking for work. Maybe if I get bored sailing?
Listening to "Just Waiting on a Friend" by the Rolling Stones.

New Holding Tank Vent Outlet

On my forward holding tank, the vent line comes out the side of the tank, and because of the small size (<1/4inch) of  the screw in fitting, occassionally becomes blocked. In clearing that blockage last year, I noticed the thread for the elbow, that screws into the tank was stripped. At the time, I secured it back into the tank with my favorite 3M 4200.
This year was the time, to replace that fitting. It was very difficult to get at, being close to the side of the hull, and I didn't want to take the whole tank out to replace it. So I came up with this idea.

I used a plastic fuel tank through hull vent that comes in two pieces. I mounted this on a 1/2 inch plywood disc, coated with 3-4 coats of epoxy. The vent has a tube within a tube and when mounted with the hose tail pointing down , gives an extra protection from water ingress (like a trap). The curved "outer" vent entry has a stainless mesh which I removed. These features, when applied to the holding tank application, should prevent fluid escaping out the vent line.

Diassembled vent and mounting disk.

The disk was located on the top of the tank and the process for attaching with epoxy glue was the same as in this blog here.  Essentially I drilled a hole big enough for the vent intake; sanded the tank and mounting disk; and applied a epoxy mixed with a silica "glue" as a paste between both parts and allowed it to set up. The vent intake was a firm fit in the mounting plate and allowed for the removal (unscrews) of the bigger vent "trap" with hose tail; and also allowed for orientation by turning the vent intake to accommodate.

Finish product

The photo to the right shows the finished product, albeit that I don't have the right type of hose. I have 5/8inch sanitation hose coming from the USA. It's not a size readily available here.
The old vent hole was closed off using a plug they use on hydraulic items. I had one come off a new transmission cooler that was the right size. And of course to keep it in there, I used my favorite product, 3M 4200. One day the tank may be removed and that will be the time to remove the old brass fitting epoxied into the tank.

You might notice the inlet to the holding tank is also on the side, (under the old vent line). I don't under stand why they were built that way. Both the vent and the inlet should be on the highest point of the tank. Next year, I might move the inlet to the top of the tank. And that will give me a couple of more flushes. Doesn't a flush beat a full house?

Holding Tank Level Monitor

 I wrote previously about Gobius Tank Level monitoring. You can review that blog here.
On my forward holding tank, there is no way to easily place an inspection hatch for level monitoring (as per my previous blog). That is because to get at the tank, I have to remove a heavy mattress and covering board to see the tank. We also use the forward berth a lot, to store our extra equipment and sometimes supplies. So it can be a real hassle getting to the forward tank.
We use to empty the forward tank whenever we emptied the aft tank; but that was a
waste of tank treatment if the tank was say only 1/4 full.
So for me the solution lay with this new tank monitor device. You can see in the three photo's, the installation of the three main components of the device. The level indicator was placed just over the head electrical switch. The "computer" was placed on the side of a locker, next to the holding tank and the sender unit on the side of the tank as indicated in their web site tank calculator. Everything was easy except the sender unit. I followed their direction to the letter, but it would not stick. Sanded level, made sure tank surface was above 20 degrees C, and wiped surface prior with their special towel. Didn't stick! They supplied a spare sticky patch with the kit, so I tried the spare. Still no stick! So I wrote to their support email and two days later got a reply. The insinuation was that I had not followed with their directions

but they would post a new sticky patch out to me. Well, that wasn't going to help much, being on a boat, "cruising the world". So I took matters into my own hand. This they didn't recommend, but I did it anyway. I sanded the sticky patch that wouldn't stick so that it had a rough surface. Next I applied a very thin layer of 3M 4200 and applied the sender unit to the tank. I had duct tape ready to tape this unit to the tank until the 4200 set up. Next morning, the sender unit was attached "rock solid" to the tank. I proceeded to change the default settings and calibrate the unit as per their directions. And the unit works great. I may at a later date put a buzzer in the analog circuit which is detailed in their instructions. In the mean time, the 3/4 warning light comes on when the tank is 3/4 full. You can add extra sender units to have a 1/4 and 1/2 level light as well, but I'm very happy with this at the moment.

Tank Fluid Measurement by Gobius

See more video here: http://ab-marine.com/gobius-video

Finally a product that requires no holes to be drilled into a tank for level monitoring. This is sure to be on my "to get list" .Gobius web site link is here. More info, and purchase can be found here at AB Marine. Read on........

Gobius measures from the outside - Nothing on the inside!

Gobius is available for waste holding tanks ... water, diesel & gasoline tanks ... industrial fluid tanks ... in stainless steel, steel, plastic, fibre-glass and aluminum
Using a totally new patented technical solution we have developed level indicators for all tanks. Gobius has been developed to meet the demand from those boat owners who want more information, those who not only want to know when the tank is full, but aso when empty.

Gobius measures from the outside

* Very quick to install and easy to use
* Coloured lamps show the current fluid level
* You avoid the struggle with taking the tank apart
* No extra drilling of hole
* No need for extra service
* Extremely low electricity consumption, less than 40 mA

* Good for everybody: boat owners and environment

With Gobius you will gain

* Knowledge of when the tank is empty so that you do not have to empty it
* Knowledge of when the tank is full and needs to be emptied
* Increased comfort and safety on board
* Everyone knows whether to use the toilet or not
* You can use the toilet when in the harbour

The Gobius technology is patented
The sensors that are placed onto the tank wall consist of a shaker and an accelerator. When the shaker creates a vibration in the tankwall, the accelerator measures the size of the vibration and passes the data on to the control unit. The control unit then starts
to calculate in order to give an exact estimate of whether the fluid
level has passed the sensor or not.

Gobius is easy to install
On the sensors there are strips of tape that are provided to attach the sensors directly onto the surface of your tank. The panel may, for example, be placed in the washroom.
The control unit is connected to the boat battery. All necessary cables and plugs needed to connect the sensors and panel with the control unit are included.

Very easy to calibrate
No tanks look the same. There are always differences in e.g. size, construction, thickness and age. In order to compensate for these differences you have to calibrate the tank before you start to use your Gobius. However, the calibration only takes a few seconds, all you need to do is to press a button while the tank is empty.

Gobius measures perfect even if there are covers (like uric salts) on the inside of the tank wall.

Extremely low electricity consumption, less than 40 mA
Gobius is constructed to minimise electricity consumption and is extremely efficient. Gobius sends power to its sensors in impulses instead of a continuous supply, thus saving your craft’s battery, 12 Volts.