Topic: Grey Waste and Water Tanks

yogibear    -- Dec-26-2009 @ 2:18 PM
  I'm just wondering whether anybody can point me in the right direction with regards to adequate sizes of water and grey waste tanks.

My current woefully inadequate grey waste tank is about to leave the building and so I was wondering what size tank would I find if I was to look under the decks of a 6 berth hire cruiser or similar?

Would "best practice" be to direct the shower and sink waste in the same direction (currently straight overboard but using eco friendly soap, children etc) or is it just the loo to the tank?

The boat is a five berth, normally full of kids, so usage is probably in excess of normal if you see what I mean(!) and the loo is a Jabsco with manual pump. There is a macerator pump inline to help get the contents to the tank...

And then there is the water tank. Currently an 80ltr Vetus bladder tank in need of filling up daily. I'm looking at a 150 ltr plastic tank. Is this excessive? (I have the room for it no problem).

Any comments - no matter how daft - greatly appreciated!

Thanks everyone,

BroadAmbition    -- Dec-26-2009 @ 2:49 PM
  Leave the grey stuff to go overboard (Shower / sink water) etc this is normal practise.

Black tank. the bigger the better as it will last longer between pump outs, if possible fit a guage / display on dash, 'B.A's capacity is around 60 x gallons I seem to remember

Fresh water tank(s) you could fit more than one with a large balance pipe joining them up, again the bigger the better as less time spent hunting for a f/w point, again a guage on the dash is a bonus. The two f/w tanks onboard 'B.A' hold around 150 gallons in total eith the expansion tank etc.

Hope this helps,


'Broad Ambition' - 'Dreams do come true' - Afloat at last 06-10-07

This message was edited by BroadAmbition on Dec-26-09 @ 2:53 PM

Aramanda    -- Dec-26-2009 @ 4:21 PM
I have just fitted the largest waste tank that I had room for on my 6 berth and as Griff said let the other waste water discharge to river. There is also some products available to put down the toilet to break down the solids in the tank similar to the porta loo's.

Stu    -- Dec-27-2009 @ 12:26 AM
  Got any recommendations as to what works best at breaking down the solids in a waste tank? My 12v loo sits straight over the tank and last time mine was pumped out I could see with the foot pedal down that there was a certain amount of solid stuff left behind.

I was tempted before doing the next pump out to get one of those long shafted paint mixing things on the drill and stick it down the toilet hole to try and break up the solids a bit.
Any thoughts?

Oh look - More rotten wood!

16E    -- Dec-27-2009 @ 8:41 AM
  First of all we are in the cassette type 'Bucket and chuck it' group and last encountered pump-out holding tanks in the mid 80's.

When Grebe was built we were advised by the builder to use Brewer's Yeast tablets in the dirty tank rather than Elsan chemicals.  The tablets do break down the solids.  The advice came with the comment "it will stink like a donkey for two weeks and then settle down..."  we did, it did.

Whether this would work if your tank has had blue in I do not know, but I suspect it might kill the yeast.


..Get on and do it!!  Adventure before Dementia.

Aramanda    -- Dec-27-2009 @ 12:07 PM
  I am sure Jabsco the marine toilet makers do something to put in the tank to break it down.

yogibear    -- Dec-27-2009 @ 2:41 PM
  Well Griff, the 150 gallons idea is certainly tempting although I reckon that's close to 700kgs and I dont have the luxury of being able to balance the old girl with twin tanks (the missus suggested that I could balance most of the weight myself as the helm is on the opposite side but my berth is on the same side and I'd end up rolling out during the night)!

I reckon I can get a decent 60 gallon in there (about 270 ltr) and the same the other side for grey waste. That'd double the current capacities....


essexboy    -- Dec-27-2009 @ 6:07 PM
    This "Stirring up" Please take a video of this, Im sure it will win a prize somewhere !

George Sims

Stu    -- Jan-1-2010 @ 11:48 AM
  I'll see what I can do. Maybe I can become the forum's official sh*t stirrer.  Smile

Oh look - More rotten wood!

ngc    -- Jan-1-2010 @ 12:08 PM
  One of the largest narrowboat hirers, Alvechurch, puts approx 1 litre of Elsan Blue in the blackwater tank after each pumpout to prevent the waste solidifying/break up any existing solids. I now do the same.

Maurice_Mynah    -- Jan-1-2010 @ 12:36 PM
  As far as the loo tank guage goes, Don't use a dip stick, is my best advice.

Honesty and Integrity ... When you can fake those, you've cracked it.

Still-Cruising    -- Jan-1-2010 @ 10:18 PM
  If you fit one of those bellows type gauges be very careful that you don’t snag the edge of the bellows during installation. If it punctures during installation it will still work for a period of time but will gradually fill up with the contents of the tank and fail. Changing one in this condition is not a fun job !!!!!.

Best Regards


Blimey that was close !

yogibear    -- Jan-2-2010 @ 12:15 AM
  Now thats a useful tip!

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