Black water lights, how do you check them

[dc380]

The lights that indicate how full the head is, don't seem to work? After 8 days at Block Island last year the half full light never lit. Is there a way to check if it's working?
If it's not isthere a way to fix it. It's a 42 gallon tank, and there is just 2 of us, but I still would have expected it to be half full after that many days.

Not that I'm looking forward to going in there, but I should go do it now while it's clean and empty.

Typically I need to get gas about ever other time out, so just pump out then, but it would be nice to know it the indicators are working.

Dave

 

[mistercomputerman]

Dave

I just had the same problem on my 42 gallon black water tank. It is said that the sender unit which screws in the top of the tank goes bad after a few years of sitting in the waste.

The replacement sender is a Tankwatch 4. It comes with and without a vent tube. You probably do not have a vent tube.

The sender comes in a 22" length and a 45" length. The sender unit has three float switch sensor tubes with floats at the end of each tube that give you the empty, hal and full readings. I bought the 45" length sender and cut the sensor tubes to match the length of the ones from the sender I removed.

Each sensor tube has a pair of wires coming out of the top. Mark all of the wires on the old sender in some fashion before you cut them so that you can hook them back up properly to the new sender.

One wire goes to the empty light, one wire goes to the 1/2 full light and the last one goes to the full light. The second wire from each tube all get tied together. The wires are hooked to the boat wiring harness. Shorting one of the three float switch sensor wires to ground will bypass the float switch in the tank and cause the respective light to light up if you want to test the wiring and the display.

The sender screws into the tank after you have cut the sensor tubes to length. You reattach the wires from the float switch sensor tubes to the boat harness and you should be good to go.

The biggest thing is marking the wires so that you can get them hooked back up to the right float switch sensor tube. Hooking the wires up improperly will, of course, make the wrong lights light up on the display.

The project took me about an hour. I would put some dish detergent in one of the heads and flush. Maybe take a ride and stir up the suds in the black water tank and then when you unscrew the old sender, it may be partially clean.

Anyway you stack it up the job stinks. Literally.

Here are some links:

http://www.dometicsanitation.com/productpages.asp?pid=53

http://www.northeastsanitation.com/...Code=600114&Category_Code=Sealand_Accessories


Good luck.

Rick

 

[jrcinnh]

You might try a good tank flush with laundry detergent first sometime that will free then up.

They are not very proportional. After a pumpout mine would light the empty lamp until maybe 10 flushes. Then no lights for a long time and many flushes. Then 1/2 full would come on and 5-10 flushes later full. On my tank 1/2 full meant emergency use only and head for the pumpout.

 

[dc380]

thanks Rick

I'll order the larger one and cut to length.

Jrcinnh

That's exactly what the previous owner said it worked. As soon as the 1/2 way light lite, he said head for the pump out.

I just don't ever remember ever seeing the 1/2 light lite. I would just pump out regularly.
Sounds like the 1/2 way senser does not go deep enough.

It looks like from the pictures the senser unscrews, so I may unscrew it and see if I can clean it.

I know sounds like fun.....

Dave

 

[estebanj]

Some tanks have the screw top (3 senders in the cap, Tankwatch 4), while others have 3 individual probes side by side. I believe the 42 gallon Sealand/Dometic tank uses the screw top 3-in-1, but check before ordering any replacements.

Esteban

 

[dc380]

Below is a picture of the tank. Based on the picture on the website Rick pointed me to it looks like I have the unscrew type.

I have one more question, since I found this picture. Are the "duck bill" in that black hose?
Is it one or 2 "bills". So far after 15 years of boating I've never had to change them, but would be a good thing to know where they are.

By the way I took pictures of the entire boat (not just the tank), because the boat is over an hour away, and these types of questions come up from time to time.

 

[sbw1]

You could also intall a monitor called Tank Tender which uses no electricity and has no moving parts and never wears out. It gives you exact tank readings and pays for itself by avoiding unneeded pump outs.

 

[mistercomputerman]

Dave

Glad to help.

Since you are going to order the longer (45") sender, you will adjust the length of each of the float sensor tubes by cutting them. Once you measure the length of the old sensor float tubes, you may want to add some length to the 1/2 tube to make it come on sooner. I think some of the units have a shutoff switch connected to the full sensor tube, so I might be hesitant to adjust the length on that one.

One gotcha-the floats themselves have an "upside" and a "downside". If memory serves me correctly the empty float goes on one way and the 1/2 and full go on the other way. It should arrive installed correctly, but......

This is a good project to read the instructions so that you do not have to take everything apart again.:thumbsup:

Two things to consider.

1. You may want to use some heat shrink spade connectors on the ends of each sensor tube wire. That will allow easy disconnection for future removal of the sensor.

2. Test the connections by manually moving the floats while someone checks the lights on the panel BEFORE you screw in the sender.

Rick

 

[Pirate]

As JRC recommended, a good flush with detergent and then let sit full of water or water/detergent solution for a week+ will usually fix that problem.

I'm rather fastidious and rigid about the waste systems. Every evening while we are staying, each head gets a full 1 minute flush to clear the lines to the tank. Every time we leave the boat, each head gets a full 1 minute flush, approx. 2 cups of the toxic blue stuff, another 1 min flush, then the tank gets emptied. If the boat will be stored more than 1 week, I fill the waste tank with water/detergent, empty, refill with water/detergent and store it full. My tank looks as if it has never been used inside and out and there is no smell at all.

We're about to cast lines and head to Islamorada.

 

[mistercomputerman]

Dave

This pump should have 4 duckbills. Duckbills come in two sizes and I am pretty sure this pump has the larger size. (Mine is the 42 gallon tank and takes the larger size). Here is the owner's manual for the tank.

http://www.dometicsanitation.com/pdf/600343562%20HTS%20Manual.pdf


Here is the manual for the Tankwatch 4.

http://www.dometicsanitation.com/pdf/600343951 TW4 manual.pdf

The duckbills are somewhere in the hoses on either side of the pump. When they go bad the pump stops pulling a vacuum which means no flushing. You might be able to get by without the head, but, the Missus is not gonna be happy doing her business over the side or off the swim platform. So, while you are messing with the tank, might as well change them out.

That Saniguard tank filter in the back of your photo is supposed to filter odors. You may want to consider replacing it also if it hasn't been changed in a while. It has two screw ends and a clamp. Not to difficult while you already have your head in the head.

Rick

 

[Sea Gull]

After you fix your holding tank issues, you might try to address the sound insulation foam. Kepping it tight against the underside of the deck will greatly cut down on engine noise.

 

[dc380]

Sea Gull do you see insulation in my picture that is loose?

That's the problem with not buying new, your are never sure how something it suppose to be connected, or was connected when it was new. I'll check it out. Hopefully it will be obvious how it should be attached.

Thanks Rick for the pointer to the manual, I just looked through the whole briefcase of documentation, and there is no Sealand documents.

The previous owner replaced the Duck Bill valves and filter for me. He had kids, and dental floss issues as well, so decided to make sure I could get home from NJ without Head problems.

So I shouldn't need to replace them now, but want to have spares on board.

 

[mistercomputerman]

Hi Dave

I just looked at your photo again and that is a picture of the macerator pump and not the vacuum pump.

While I am pretty sure that the macerator has duckbills too, it is the duckbills in the vacuum pump that create the suction for the head itself.

Just wanted to clarify.

Rick

 

[dc380]

Thanks Rick

Yes, the manual you pointed me to shows the actual vaccum pump which I recognised as, being located to the right of the picture.

It mentions the gauge opening doubles as an inspection port. Now I have to admit I have never looked in a holding tank, but I will be this month! It looks it's may to be easily removed. I hope I did a good job of rinising it out last fall.

I definitely will try giving it a good flush come May 1 when the pumpout station opens.

It has a maserator like you said, but I don't go anywhere with the boat where I can use it.
I think the only place left is South of Montauk in the open Ocean.

Dave