Sealing the Holding tank sensor

[maxumaa]

I detected a odor from our holding tank. When I checked I saw that the tank had a "belly" in the top. I suppose from a strong pump out pump. The tank monitor is mounted in a hard plactic plate. The belly in the tank caused a gap between the plate and the tank causing the smell. I tried sealing it with Boat Life caulk but I can still smell it around the fitting. Is there a different type of caulk that should be used to contain the smell? Any other suggestions? Thanks in advance.
KO

 

[Vic Willman]

Most tank monitor sensors or floats screw into a threaded hole. You might be able to tighten it down some more... Is the tank plastic or metal?

 

[PascalG]

i see you have a maxum 35. i had a similar problem on my old 98 maxum 37 where a clogged vent filter caused the tank to collapse. so check your vent filter and replace if it's original.

the collapsing had caused the wire for teh sender to pull out and the whole boat stunk. i was able to pull the fitting and reseal/reconnect the wire but it wasn't a plate. any sealant will work but you will need to pull the plate and reseal it completly.

i dont' know where the tank is on the 35, but on the 37 it was behind the head, under the stair, next to the mid cabin in a large space with the pumps, water heater, etc... that space extended all the way to the port hull side and fairly high above the side deck so i added a vent about 10" above the side deck. it helped a lot venting this space. i drilled a 2 or 3" hole next to the head blower exhaust vent cover and put the same cover in.

sooner or later you'll get some smell in there, just with hoses aging, venting it is easy and helps a lot.

 

[maxumaa]

Vic, The tank is plastic. The plate has screws in the 4 corners and the screw into the plastic, not a good seal. Don't want to crank it too much. It will just strip the plastic.

Pascal, I did actually by pass the vent filter temporarily. I just wanted as much air flowing in/out as possible. I did remove the plate and seal it and screw it back down. 3 weeks later if I get close I can smell the ordor from around the sensor. That's why I thought maybe there's a better selant to use. The tank is under the bunk in the mid cabin. I guess I can vent the area as you did but I still need to stop the leak from the sensor.
KO

 

[PascalG]

under the bunk ? so it will be hard to vent... on the 37 it's above the bunk, behind the panel.

these odors are hard to eliminate, what you want to do is see if it's worst when someone flushes and air is expelled. if you dont' smell anything worst after flushing, then i wouldn't worry about it.