Black Water Tank Venting

grandaddylow

Member
Joined
May 21, 2020
I've decided to go down the route of a larger black water tank with a marine toilet. I'm looking for enough capacity to do a week of grid for 5 people, so cassette toilets are out.

Does anyone have any advice on venting black water tanks? It rather looks like it has to be vented to the roof. I'd like to minimise the number of holes in my van - is there any cunning solutions out there that negate the need for roof vents?

Thanks, GDL.
 

Sandbagsid

Active Member
Joined
Sep 16, 2019
Only problem with a large waste tank is the amount of weight once it’s half full or more, it will eat into ya load carrying capacity. I think you have to vent then above roof height for smell even then if the winds in the wrong direction it could be a bit toxic. You might be able to get something similar to a domestic dergo valve As used on house soil pipes that way it wouldn’t have to go to high up, just a thought. Good luck getting it sorted.
 

grandaddylow

Member
Joined
May 21, 2020
Weight is not an issue: I deliberately bought a 7t van so that I could carry enough water for a week.

I too wondered about the dergo valve, but they seem to admit air into the system rather than permit gas to leave. I think if I modified it to be two way, it'd probably leak more than gasses...
 

BigStevie

Active Member
Joined
May 17, 2017
Location
Highlands
I used a stainless steel marine fuel tank vent high up on the body side to vent the leisure batteries. Neat and cheap!
Might be worth to see how manufacturers deal with venting black water tanks, have a look at some a-class camper designs/manuals?

Stevie
 

grandaddylow

Member
Joined
May 21, 2020
The RVs and boat people are using pipes with ID over 1.25 inches. Straight is apparently desirable as it makes it easier to clear blockages. I think I'll have to bite the bullet and cut another hole. Cutting holes in vans always feels a bit 'wrong'!
 

Ballcock

New Member
Joined
Sep 3, 2017
A Dergo valve is an air admittance valve not a vent it is to allow the soil pipe to flow without causing a vacuum. Could you run a small vent up the outside of the van if the waste tank is mounted underneath. it would not need to be a large diameter so could easily be run up along a ladder or even a flat oblong section up the rear quarter.
 

roadliner

Active Member
Joined
Apr 22, 2018
Location
Peak District, Derbyshire
The RVs and boat people are using pipes with ID over 1.25 inches. Straight is apparently desirable as it makes it easier to clear blockages. I think I'll have to bite the bullet and cut another hole. Cutting holes in vans always feels a bit 'wrong'!
When you have cut bloody great holes in your van for windows ,roof lights etc. a pipe is nothing. Go for it!
 

grandaddylow

Member
Joined
May 21, 2020
Yup. Your probably right. I'm worried that a narrow bore will clog. The boat people reckon that straight pipes are better cos it's earlier to shove something down it to unblock it...
 

Sandbagsid

Active Member
Joined
Sep 16, 2019
Bit of 32mm plastic waste pipe with a tee piece on top facing front to rear so the wind would blow across the top getting rid of any smelly stuff
 

tacr2man

Active Member
Joined
Dec 13, 2017
Location
Near J10 M40
Why marine toilet , cant you locate black tank below the toilet , most RVs are direct or near enough entry . Then you need to be able to position your grey tank to feed into the black dump pipe to flush it when dumping .
 
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