Holding tank over winter

[Mandj]

Our first 'boating winter',

Our holding tank is around a quarter full but struggling for time to pump it out (Pump out at another marina etc..)
Will the chemicals in the tank prevent freezing, and/or is there any issue simply putting the pink 'antifreeze' through the toilet system and into the tank.
My wife mentioned the risk of mixing chemicals...

Many thanks in advance..

 

[Momac]

Perhaps a frost protection tube heater on a thermostat in the vicinity of the holding tank might be considered.

 

[Mandj]

Thanks Martin,
I had thought of this but have an issue with space around the tank.

 

[harvey38]

Intrigued, what and why are you putting chemicals into a holding tank?

 

[Mandj]

When it was last pumped out, a blue solution was put in to the empty tank (I believe to be ready to breakdown the matter) along with a pink coloured freshener ..

 

[oldgit]

Location of boat , in or out of the water, fresh or salt. ?
Would be more worried if boat out on the hard, have known water in Mercruiser exhaust risers to freeze and to crack cast iron.



Chum put a couple of temp sensors in his Pedro, one in the bilges and one in a cabin.
No heaters turned on.
Cannot recall if any hatches or vents were left open to aid airflow.
Every 60 mins 24/7 over week or two they recorded and logged the temp in C .
The boat was in a freshwater marina on the Thames , might have been Windsor or Bray.
No obvious flow of water in the marina.
Even during winter weather even when there was layer of ice on the surface of the water did the bilge temperature fall below 7C.

If in salt water with any sort of flow , would doubt that under normal circumstances water in the holding tank would freeze, unless a very long period of sub zero temperatures forecast, in which case a trip to the boat and mebbe a small tube heater employed.

 

[Mandj]

Ma

Location of boat , in or out of the water, fresh or salt. ?
Would be more worried if boat out on the hard, have known water in Mercruiser exhaust risers to freeze and to crack cast iron.



Chum put a couple of temp sensors in his Pedro, one in the bilges and one in a cabin.
No heaters turned on.
Cannot recall if any hatches or vents were left open to aid airflow.
Every 60 mins 24/7 over week or two they recorded and logged the temp in C .
The boat was in a freshwater marina on the Thames , might have been Windsor or Bray.
No obvious flow of water in the marina.
Even during winter weather even when there was layer of ice on the surface of the water did the bilge temperature fall below 7C.

If in salt water with any sort of flow , would doubt that under normal circumstances water in the holding tank would freeze, unless a very long period of sub zero temperatures forecast, in which case a trip to the boat and mebbe a small tube heater employed.

Many thanks - that’s really useful.
The boat is in the water, in a marina on the Norfolk Broads, so generally fresh water.
I have put tube heaters in the bilge but sadly the holding tank is under the berth in the aft cabin so tricky to get a heater to.
Your post does give reassurance however ?

 

[Farmer Piles]

I inherited a part full holding tank when I bought my boat last winter and it has been making hideous smells all season. I tried to empty it but to no avail. Since the boat has been ashore I have ripped out the panels to get to it and found a fibreglass Vetus tank of about 60 litres, half full of fetid stuff that was at least 2 years old as the previous owner had not used it.. With uncovering it I managed to get the liquid out and then lugged the tank out of the boat with a 3 inch layer of sludge in the bottom. The smell was unreal!! Like rotten eggs on steroids. Now in the process of replacing all the old pipework and sorting the whole mess out.