Breather pipe diameter

[Sea-Fever]

Hello again....

Tek tanks website states breather pipe plumbing for a holding tank should be min. 38mm.

They also recommend active carbon filter.

Vetus (via ASAP) supply a range of filters but only the largest has a 38mm connection.

Does the venerable community gathered here have 1.5" breathers on their holding tanks?? Or will a smaller diameter do quite nicely without causing anaerobic putrefaction...if that's the right term.

 

[Sea-Fever]

In fact ASAP do not appear to stock the 38mm replacement filters but do stock the filters for the (more common?) 16mm connection filter.

 

[MoodySabre]

I have a Tek Tank and a 38mm Vetus filter with carbon filters inside it. I have never had any bad smells from the vent clamshell fitting. I assume that the Tek tank will come with 38mm hose fittings unless you specify smaller.

I bought mine direct from Vetus.

 

[RichardS]

In fact ASAP do not appear to stock the 38mm replacement filters but do stock the filters for the (more common?) 16mm connection filter.

I'm sure that my holding tank breather is around 16mm, maybe 19mm.

38mm sounds like the hose carrying black water to and from the holding tank.

Richard

 

[pvb]

There's a theory that the breather hose has to be a large diameter in order to allow fresh air into the holding tank to prevent smells. I'm not sure what causes fresh air to flow into the tank; I suspect there isn't a lot of air movement regardless of hose diameter. On that basis, I reckon the smaller diameter hose is sufficient.

 

[Sea-Fever]

I suppose if you have a manual pump between the outlet of the tank and the seacock this sucks clean air from the breather rather than water from the heads???

 

[Sea-Fever]

I have a Tek Tank and a 38mm Vetus filter with carbon filters inside it. I have never had any bad smells from the vent clamshell fitting. I assume that the Tek tank will come with 38mm hose fittings unless you specify smaller.

I bought mine direct from Vetus.

That's one vote for 38mm breather

 

[Sea-Fever]

I'm sure that my holding tank breather is around 16mm, maybe 19mm.

38mm sounds like the hose carrying black water to and from the holding tank.

Richard

And one vote for 16mm or thereabouts

 

[VicS]

And one vote for 16mm or thereabouts

I think if you fit a filter it will restrict the ventilation so much that you might just as well forget about trying to maintain aerobic conditions and use 25 or even 16mm hose for the vent line.

 

[Forty_Two]

38mm also good if you use a powerful shore pump out, to avoid collapsing the tank with the suction.

I have the Vetus 38mm breather filter. Never had a problem with smells or replacement filter elements.

 

[Sea-Fever]

I think if you fit a filter it will restrict the ventilation so much that you might just as well forget about trying to maintain aerobic conditions and use 25 or even 16mm hose for the vent line.

Hmmm.... I see .... so maybe a filter is appropriate for smaller breathers because it may become anaerobic.... And perhaps less important for larger breathers

 

[Plum]

Hello again....

Tek tanks website states breather pipe plumbing for a holding tank should be min. 38mm.

They also recommend active carbon filter.

Vetus (via ASAP) supply a range of filters but only the largest has a 38mm connection.

Does the venerable community gathered here have 1.5" breathers on their holding tanks?? Or will a smaller diameter do quite nicely without causing anaerobic putrefaction...if that's the right term.

If you go to a marina with a pumpout facility if the breather can not allow air in as fast as the pump can suck, your tank will collapse so a breather of the same bore as the pumpout fitting makes sense. If you only ever empty your tank offshore using gravity or a hand pump then a smaller bore breather should be ok.

www.solocoastalsailing.co.uk

 

[BabaYaga]

I suppose if you have a manual pump between the outlet of the tank and the seacock this sucks clean air from the breather rather than water from the heads???

For a pumped discharge system, the discharge pipe must be taken from the bottom of the tank, either externally or by a dip tube.
My breather pipe is 19mm, no filter and no smells. Suction at pumpout stations is normally not a problem, but occasionally it is quite strong. Certainly not strong enough to make the tank implode, but clearly flat panels are affected. Not sure it does the welds any good (stainless steel tank).