What’s that smell???

For some time Maria has been complaining that’s there is a funny smell in the saloon. It’s not there all the time and is sometimes disguised when the air freshener goes off but Maria wanted it traced. I either have to investigate the smell or buy Maria, and any guests, a nose peg!

Our friend, Mark from Motion, was on board and offered to help but little did he know that we would be doing this for hours!

We had already worked out that the smell wasn’t the grey water system and also wasn’t coming from the bilge.  When we lifted the floorboards around the holding tank, IMG_5866the smell was more pronounced. Oh dear, this is going to be nasty.  Inspection around the holding tank showed that there was no leak, that was a relief. We also knew that the holding tank was empty since we had emptied it a few weeks ago. Over the last few years we had changed a lot of the pipes, hence the white pipes in the picture. The creamy coloured pipes are the remaining pipes but these appeared to be fine with no smell coming from them.  We decide to try and trace where any gas is escaping the system by putting a fairy liquid solution across each of the pipes and around the top of the holding tank.  This reveals that the “gas” is escaping from around the sender unit that shows whether the tank is full or not.  It also revealed a small split in the pipe that led to the sea discharge, maybe this was enough to let the smell out? Rather than replacing the new and clean pipe we decided to put in a join and replace the split part with a new short length of pipe.  This was uneventful, having heated the new pipe in a pan of hot water for a couple of minutes to ensure that the 38mm pipe went onto the 40mm fitting on the holding tank…. a snug fit! But we were not convinced that this constituted the full extent of the problem. We then decided to add some water to the tank and discovered that the tank was under pressure when I opened the pump out and heard air hissing.  The setup on the Moody has two inputs from the two toilets, a deck pump out, a sea discharge and finally a breather pipe. With a breather pipe which works both ways, there should not be any pressure.  This led us to do some investigation on the breather pipe to try and understand why there is pressure.  Firstly we wanted to check that the breather pipe in the holding tank didn’t have a long downpipe (I.e. That the breather wasn’t connected to the pump out by mistake. Having checked which pipe was which and removed the tank inspection panel, it was time to hold your breath and open every window on the boat! That is definitely the smell…. but the pipes are the right way round – quick put it all back together again! Consulting the owner’s manual revealed where the breather pipe left the boat and it was interesting to see that this was a smaller pipe than the inch and a half pipe leaving the tank. A reducer somewhere perhaps? It also appeared that there was a join with another breather pipe…very confusing.  The breather pipe goes forward and we can see it doesn’t come back at hull level, so maybe The return is high and is in the headlining? Removing fifteen screws allowed us to check that this wasn’t the case! Great now to put them all back again.  But we are still confused as to how the breather is working.  We decided to force air into the breather using a footpump from the tender. There was a bubbling coming from the sink! The grey water system linked to the black water system for a breather??? Surely we would get foul smells from the sinks.  IMG_5865Tracing back the pipes revealed that the join in the breather pipes was from both grey water boxes and wasn’t linked to the black water breather at all. Back to the manual….and tracing the breather pipe forward behind the TV and up further forward. Check the hull to find a second breather, so the manual is incorrect and the pipe runs further forward. Ps, this breather isn’t the fuel breather which is adjacent to the fuel cap or the fresh water system breathers which are in the cockpit…

So we seem to be checking for a blocked breather.  Using the footpump from within the boat and we are able to push air out but it seems to take a lot of pressure. Filling the holding tank up with fresh water through the pump out resulted in water coming out of the breather.  But we have not been able to force air or wate into the breather from outside the boat.  Our current theory is that there is a flapper valve which stops water getting into the system but since it won’t have been serviced or replaced in fifteen years, then maybe it is stiff, blocked or jammed.  Our investigations continue but for the moment we don’t understand why the breather is not allowing the system to stay equalised.

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