DRAGONFLY Trimarans User Forum

When trying to empty the holding tank on the new to me DF 35 with the macerator (sp?) pump, the holding tank gauge does not go below 15%. Normal?

Should head switch me on closed or open?

Thanks!

Do not run the macerator pump dry. It contains rubber vanes (like the engine's raw water impeller) that will disintegrate if run dry.

Not sure what you mean by the head switch, but you just need to open the outer through-hull to pump overboard. The tank vent will prevent a vacuum.

As for your 15% reading -- perhaps your level sensor is stuck?

Thanks Larry. By the head switch I meant that lever next to the hand pump at the toilet bowl. If the holding tank has a vent (where does it come out?) then there is no need to do anything.

I guess my next step is to use a marina pump-out and see if the sensor moves to zero. If yes -- investigate macerator pump, of no -- investigate the sensor.

Oh the joys of boat ownership!

Mine also shows 15% as minimum, even when the macerator pump is sucking air. It showed 0% when the boat was new so I think it is necessary to clean the sensor. Read an article in a magazine describing this problem, and plan to clean the sensor during Eastern.

The holding tank is vented through the outlet of the sink. If the vent is closed, the macerator pump will suck the toilet empty of water.

According to the manual the pump can be run dry. If this is wise, I don't know.

Pumped out the holding tank yesterday, it showed 15% anyway. Then filled it with fresh water and pumped out again (twice). Shows zero now.

When I first got my DF35, I noticed this and queried with the yard. They told me that you have to hold on the pump for quite some time to make it show zero. I.e. it may feel like its pumping dry but its not.
One other feature of my DF35 (no.25) was I noticed that while sailing, the holding tank actually filled up with water. Apparently a number of boats were fitted with the pump the wrong way round which created a siphon effect while under way. This could be remedied by reversing the pump and also reversing the hoses. I chose the easier (lazier?) option and now keep the valve shut unless I need to pump out.

Cleaned the sensor yesterday and system shows 0 again when the tank is empty.
Had to remove a lot of salt deposits on the float and on the inside and outside of the perforated protection tube around the float . A hard and sharp plastic scraper is the best tool to do this, when the sensor parts are submerged in water.
Removing the sensor is quite simple. Disconnect the blue and black wire in the junction box on the tank and unscrew the screws for the sensor. Then it's just to pull the sensor out of the tank.
Wondering if leaving the tank 30% full of freshwater at regular intervals would help to delay the next time this job is has to be done? Even if it's simple it's not exactly pleasant.

penryj wrote:When I first got my DF35, I noticed this and queried with the yard. They told me that you have to hold on the pump for quite some time to make it show zero. I.e. it may feel like its pumping dry but its not.
One other feature of my DF35 (no.25) was I noticed that while sailing, the holding tank actually filled up with water. Apparently a number of boats were fitted with the pump the wrong way round which created a siphon effect while under way. This could be remedied by reversing the pump and also reversing the hoses. I chose the easier (lazier?) option and now keep the valve shut unless I need to pump out.

Here in the USA you can receive a heavy fine if you are caught with the valve open unless you are at least 3 miles offshore in the ocean. It must be closed anywhere in Long Island Sound because it's not legal to pump overboard there. Even more than that, the valve must be "secured". That means it must be locked, or secured with a zip tie or wire, or the valve handle must be removed.

Einar Gloersen wrote:Wondering if leaving the tank 30% full of freshwater at regular intervals would help to delay the next time this job is has to be done? Even if it's simple it's not exactly pleasant.

I was thinking the same. Filling the holding tank with fresh water a few times helped, but the sensor still has the tendency to set stuck at 15%. I am thinking of filling it with fresh water and adding some urine stain removal liquid they use on toilet bowls and such. Just need to find one that wouldn't dissolve the hoses... http://www.whink.com/product_info.php?c ... ucts_id=33

Pouring in lemon juice or coca-cola (yes!) may work too. I think I may try these first...

found a recent thread with pictures http://www.dragonfly-trimarans.org/phpB ... .php?t=456

The problem with using acids or corrosives is that many of the parts are stainless steel and they will be attacked if those materials are left sitting. Even urine will cause enough corrosion to eat through stainless holding tanks. The stainless DF-1000 tanks I know of have needed replacement after about 10 years due to leaks. My 1200 holding tank is from 2001 and I'm planning to replace it this year, because I think it's only a question of time, and I'd rather do it before a problem happens.

As for the sender, there are non-mechanical designs that do not use a float. I switched mine, which also required me to switch the panel display at the same time. I'm currently using a Xintex level indicator and it works more reliably, although I don't like it because it's not accurate when there is a lot of boat motion. It uses two wires to the sender so I could use existing boat wiring.