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      The FW pump in the aft cabin has been noisy since purchasing the yacht in Jan 2021.  In May this year it started to power up intermittently even with no taps running.  Could not find any leaks so “temporarily” kept the pump switched off except when water was needed.  Skip to mid-July and, for the first time ever, there was water in the bilge by the sink (where the bilge pump is situated) and running through to the foot of the mast through the connecting holes. Tasted the water to check and it is definitely FRESH. Drained as much as possible out with the bilge pump and then dried off with bucket and sponge – in total, about 20-25 litres.  Despite a moderate rain storm the night before, realised this quantity of water could not possibly have come down the mast but still could not find any leaks.  Bilge stayed dry until until I again found similar amounts of water late last week. Note: the pump is still operating intermittently without demand. Having checked along the system for leaks I lifted the aft cabin under-bed board to look at the pump and noticed:

      1. only 2 of 4 screws holding the pump to the bulkhead were fully home – may explain the noise when running.

      2. A trickle of water from the aft FW tank lid – begins to explain the leak

      3. A significant bulge/swelling in the aft FW tank sufficient to have lifted the under-bed board.

      4. The aft FW tank has split from a short section of the hull.

      I immediately opened the filler cap on the transom and there was a significant release of pressure.  The aft FW tank returned to normal size sufficiently for me to remove the tank lid. Turned on the pump and taps to partly drain down the tank, turned the pump off to prevent burning out, cleaned up the tank lid seals and replaced.  The pump is still operating intermittently without demand (every 2-3 mins). All this is a temporary solution to prevent any further leaks whilst away from the boat for a few days.

      It would seem, somehow, that the pump may be causing a back pressure in to the aft tank – which is baffling as it is still delivering water to the taps and transom shower.  I have been through all the pump/water tank posts on the forum and cannot find anything beyond tightening the pump screws to reduce the noise.

      Any help or advice greatly appreciated.  Thanks in advance.


        The curious thing here (your very detailed report is most helpful) is the expansion of the FW tank and the rush of air when the filler cap is opened. This sounds to me like a breather issue. There must be a breather to let air into the tank when water is pumped out. Is yours blocked or even removed.
        I have a 2003 B32, not 36, and I have to note that I am not sure where the breather is. There must be one though.
        You probably have the same pump as me. They are noisy. When I had fresh water in the bilge there were 2 issues: minor leaking from the pump itself (cured by stripping down and refitting with gasket sealer) and leaks from one of the pipe junctions near the pump.
        The pump has a strainer which can be unscrewed and cleaned out. Mine was clear after 18 years’ use.

        Hope this helps.

        Jonathan (


          Thanks for the quick reply.  Having crawled around in the sugar scoop space aft, there does appear to be a breather or relief pipe but ….. it terminates just inside the filler cap so once the cap is on, no air would get in.  I’ve inspected it but only to ascertain if it was some kind of jury rig and it seems to be as built. As far as the pump is concerned, the noise itself is not so bothersome, its the fact that the pump operates every 2-3 mins even without demand so for me to get any sleep, I have to switch it off.


            <p style=”text-align: left;”>You have 2 problems, then:</p>
            1. The blocked breather – should be easily addressed.

            2. The pump coming on all the time. Save for the remote possibility of a duff pressure sensor in the pump this can only happen if there is an air or water leak somewhere. Given that you have fresh water in the bilge you certainly have a FW leak. From what you said about the state of the tank you may have an air leak as well as a water leak. Both can be a struggle to deal with but at least there is near certainty that you are looking for leaks, not pump issues.

            It is worth checking your transom shower. I keep meaning to permanently disconnect mine (little need for it in Fleetwood); check the tap is off and that there is nothing coming out of the shower head.


              Many thanks Jonathan. Fairly certain the water is caused by over pressuring of the tank, in turn causing leakage from the cap on the tank – the pressure was so great at one point that water was also leaking from the filler cap fitting on the transom.  What I don’t understand is how the tank is becoming pressurised.  If the breather (if that is what it is) was blocked, that would cause a vacuum as water was drawn from the tank and I’d expect that to result in taps/shower not working …….. unless it is a duff sensor and that is causing the pump to pressurise (every 2-3 mins) when there is no demand.  I will start with an air leak search and then move on to a strip/clean/repair of the pump/gasket/strainer.

              As an aside, we are finding the transom shower a godsend this summer, as we don’t have an internal shower (previous owners removed) – exploring the S Coast / Scillies / Channel Islands and it’s definitely warm enough for a swim! Thanks again. Chris


                I see. Pressurisation to that extreme extent suggests a duff sensor in the pump. Regular pump activation along with FW leaks is the common problem – obviously the leaks cause the sensor to call for more pressure. But extreme pressure in the tank must be a duff sensor. When I had mine our for a strip-down I noted the model number and a new replacement is still available at a not too excessive price. Given the original’s age and the severity of the problem you might save yourself hassle by simply replacing the pump.


                  Thanks for your help.  I’ll look for a new one and, in the interim at least I have options to strip/clean.

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