Holding Tank Air Vent

[PaulN]

When our holding tank gets to about half full the is an external foul smell coming from the vent which is embarrassing when moored in close proximity to other craft. 

Has anyone else experienced this please and what is the solution. Is there some sort of filter I can add to the vent hose for example. 

Any help will be appreciated. 

[Smoggy]

You can get a carbon/charcoal filter to fit inline.

Or drink less beer....... (get the filter!)

[BrundallNavy]

There is probably sludge in the bottom of the tank which is being stirred up when liquid is added. The tank needs a good clean out.  
 

 

[OldBerkshireBoy]

12 minutes ago, BrundallNavy said:

There is probably sludge in the bottom of the tank which is being stirred up when liquid is added. The tank needs a good clean out.  
 

 

Isnt this more likely when the tank is empty,it is harder to stir up sludge laying in the bottom by adding more liquid when a tank is half full of liquid.

[OldBerkshireBoy]

Adding a filter may help mask the problem but it is not the cure. Would clean the tank instead.

[MauriceMynah]

When the tank gets to that stage......  Moor up close to people you don't like.  :-)

[Vaughan]

Are you using toilet blue?  This should reduce odours.  Trouble is these days, some people say it doesn't Save The Planet!

[Meantime]

They may not thank me if it's that bad, but go to Sutton Staithe for your pump out. Best on the Broads with more than one rinse if your tanks in a bad way.

[BroadAmbition]

Agree with Sutton Staithe - they really go to town on the rinsing

We have a Vetus in line charcoal filter then onto a hull fitting.  It's a biannual maintenance item for me to remove the charcoal pads, clean / dry refit.  Never had an issue, only time it has got smelly is if the tank is approaching brim full which we avoid happening most times

Griff

[JanetAnne]

It's lack of chemical (blue). I'm afraid that splash of blue in half a bucket of water you get at some yards is totally inadequate. Not only is it a bit tight it also does not take into account the size of the tank it is treating. A 200ltr waste tank needs double the dose a 100ltr tank requires but everyone gets the same dose irrespective.

If your tank is beginning to hum a bit at half full just double the amount of blue at the next pumpout and see how it goes. The chemical itself normally has a dose guide on the bottle, you'll be surprised. 

Nothing wrong with charcoal filters but you may be masking the problem rather than dealing with it?

[PaulN]

Thank you to everyone above for your valued assistance (although Smoggy's solution of drinking less beer was a bit too radical for my liking)

We had a pump out at Sutton Staithe last week and you are right. This was the best pump out we have ever had, with the tank being thoroughly flushed. Surprisingly, Eddie who did the pump out had been following this topic on the forum and was pleased with your comments. 

We always use blue, but have bought some more so that we can double dose in the future.

Today I have ordered 2 Vetus waste tank breather carbon filters, as recommended by you, which seem the best opinion due to compact size and the fact that the carbon element can be replaced.

Unfortunately I've had an added expense, as my tank has 2 25mm vent outlets. Having spoken to the boats builder, this is because the tanks size (80 gals = 363 litres) needs a minimum of 38mm vent and there would be inadequate space to bend the pipework at this diameter, it therefore has 2No. 25mm vents.     

Thanks again everyone, you will soon be able to moor next to me with your windows open 

[Jbx5]

Good information this as I have the same problem with a smelly waste tank vent when half full . (The boat didn’t have a vent when manufactured  don’t know why ? Is it really needed ? which was only 10 years ago but was picked up on survey when we bought her 6 years ago so as it was an nya stock boat done without any bother ).
I don’t think it has any inline filters so will address this as well. It is also a big tank 220lts so extra blue bought yesterday. When we have a pump out it takes quite a while and we get looks a bit like the McDonald’s adverts believe in getting your money’s worth!
Because we use the boat for odd days rather than full weeks it’s not pumped out every week like others may do which doesn’t help.  

We are also moored just down from you in the same marina Paul so it will be getting a smelly reputation😂

John

[PaulN]

High Jbx5

I don't see how the tank can work properly without a breather, as when you use the toilet the air in the tank has to be displaced and the only way yours can be is back through the toilet pan.

Likewise when being pumped out, how can the air get back in the tank other that via the toilet which should be sealed either by the closed off outlet in the pan or a water trap similar to a domestic toilet.

Not sure which is your boat, but will have a good sniff next time I walk down the pontoon to my boat!!

[Heron]

Your pump out taking quite a while might be down to an old pump out suction pump rather than the volume in the tank. Modern pumps empty a holding tank very quickly these days, but they cost lots of money to purchase and install. (Assuming a yard can actually find one these days!)

[PaulN]

As I said in my last post, I decided to purchase 2 No. Vetus filters for waste tank breathers as advised by Griff (Thanks Griff). These are fitted under the starboard deck behind the double bed headboard.

Attached is a picture of the end result.

Griff, you say your maintenance is to take out the filters, clean and dry them. Does this mean I don't even need to replace them every couple of years.

Thanks everyone for your help, my wife and I are now looking forward to our 'Sundowner' on the stern deck, enjoying the fresh Norfolk air.

[BroadAmbition]

That looks a proper neat job you have got installed there - Nice one.

They are the same ones as we have fitted.  My cleaning routine biannually is to remove the charcoal pads, gently wash them in warm soapy water, leave them to dry naturally (Not forced) then pop them back in

Ours are now 14 years old and as good as new

Griff

[Smoggy]

If you have any vent fittings on the other side of the boat you could swap one over so the holding tank has a vent each side, this would always give a slight flow through of air in even low winds.

Not worth having more holes though if no fittings already there.

[PaulN]

Thanks Griff, having thought it through in advance, it only took me a few hours to install. I will adopt your regime for cleaning, I had no idea that this could be done. All these parts were ordered online from asap supplies and delivered free 48 hours later, great service.

Thanks smoggy but as the photo shows, both vents are on the same side of the boat, any other route would be a nightmare.

[SteveO]

We had this problem and learned a couple of things that are worth repeating here. One was that, depending on the architecture of your waste system, "blue" introduced via the pump-out hose may not actually ever make it to the tank. Our tank is on the starboard side of the boat and the pump-out is on the port deck, which means that there is a long transverse length of pipe crossing the boat at bilge level. If not carefully back-flushed into the tank, the blue will just sit in the pipe until the next pump-out. For this reason, I tend to add the blue via the heads and pump it into the tank from there.

The other point is the diameter of the vent pipe, which I believe the BSS stipulates as no less than 12mm. The only problem is that over the passage of time, a 12mm pipe can become significantly narrowed, especially if the tank is overfilled, leading to anareobic conditions, which produce the smell. We had ours replaced with a 1.25 inch pipe with appropriately sized fittings at either end. The result is a properly vented tank which stays in "aerobic" mode and doesn't emit a noticeable odour.