Mystery Servo Sound - Holding Tank?

[spoondrift]

We are new boat owners this season, and learning some of the quirks of our '82 Catalina 27. Ever so often (every few minutes), we hear a quiet sound coming from under our v-berth. It sounds of some kind of small motor. Or pump. It makes a very quiet whirring noise like an electronic servo. It seems to run even on aux battery, when all other power is off.

At first we thought it might be the bilge pump doing its thing, but quickly realized that's a different sound (definitely works -- and triggers less often). This sound is loudest toward the front of the cabin and low. Opening the bilge cover makes it a little louder but confirms it's not that pump. Opening the v-berth panels confirm it's coming from that area, where our holding tank is.

We haven't used our toilet except once since we put in, but we have flushed some freshwater through to test out the jabco, and it worked fine. Obviously, our head-use seacocks remain closed most of the time (we are inland-coastal based, so just freshwater to pump in to flush). Any idea what it could be? Macerator? Pump? Help! Thanks.

[colemj]

Do you have a small bilge pump in that area? The automatic ones without a float switch turn on every few minutes for a couple of seconds to check for any water.

A bilge pump would ideally be wired direct to the battery and still work when the switch is off.

Mark

[Paul54]

I have a Catalina 36 which I am sure is layed out different. The pump for my shower drain is up under the V berth. Most of the Catalina's have a very strong users group with a wealth of information. I know there is one for the 36, 34, and 30's. should be one for the 27's. See if you can find it. You won't be disappointed.

[Paul54]

International Catalina 27/270 Association

[rhubstuff]

Anything that makes a noise is drawing current, so check your battery draw while the noise is "on" to see if the sound is coming from something on your boat. Or disconnect batteries and see if the sound still happens. It might be coming from another boat nearby. Bow thrusters especially can be heard quite a ways under water.

[BentP]

Could it be you have an ultrasound level sensor in that tank under the berth?

[kelbylinn]

Do you by chance have a fresh water pump that may be catching up on pressure once in a while? Another thing that could randomly run...

[HopCar]

My two suggestions are as Mark pointed out, a Rule bilge pump that turns on briefly every two or three minutes to check for water.

As Kelby pointed out the second thing that turns itself on is your fresh water pump. If there is a leak in the line or bad valves in the pump, it will turn itself on at regular intervals. Bad valves are pretty common and it can drive you crazy.

[Stu Jackson]

I am confused. You have the boat right in front of you. Could you not take the cushions off the V berth, take out the covers over the hole, and get a flashlight?