Vacuflush – Replacing Seals and Ball Flush

Sealand Vacuflush 4800 Series

Every now and then, more now than then at the moment, there are jobs that simply must be done. Jobs that test a man’s courage, sense of smell and just about everything else imaginable. OK, ok, so it’s not that bad but recently, after changing every single duckbill in every single location on the boat (8 x 2 inch Duckbills and 4 x 1.5 inch Duckbills in all) the good old M-Series vacuum pump was still cycling more than I would like, about once an hour. As such, I decided it was time to replace all bowl seals and flush balls. But how?

As is usual, I decided to go to the all-knowing YouTube for help but alas there was nothing there other than a single video of some chap with his back to the camera covering the most important details rendering the video totally useless. Urgh…… As such, I decided to document the following in the hope that it may be useful for those who find themselves in the same situation.

Before I start two things worth mentioning, 1./ Sealand suggest replacing seals and flush balls every three years but that does not apply to live-a-boards, as such ours will now be replaced annually and 2./ for those with the M-Series pump don’t forget to change the diaphragm and oil in the pump annually – and yes the M-series does have oil in it!


Pendana’s head system

Diagram of head parts

If we go to the instruction manual all looks pretty simple and straight forward Sealand suggest the following steps below.

Replacing the seals

Replacing the flush ball

So in pictorial form this is what it actually looks like. (NOTE: Do not forget you will need a 7/16in deep well socket to complete this job!)

The job begins!

Loosen the two screws holding head to base

Carefully lift head off mounts

Check to see you have enough hose and cable before moving to far – if not, disconnect

Place head upside down

Remove main assembly – note 7/16in deep well socket

Carefully lift

Place sideways to allow access to drive-arm and undo four mounting screws

Loosen hex nut on rotor shaft cam (honestly who comes up with the names of these things)

Gently ease drive arm board from main assembly

Perfect, it’s off!

Rotate flush ball to gain access to locking screw and undo

Rotate flush ball back to remove

With slight pressure (pinch) remove flush ball

Remove old flush ball shaft

Its out! NOTE: the two O-rings. *IMPORTANT* Loss of system pressure without losing bowl water can occur at this junction

Place new shaft in hole and replace flush ball

Rotate to gain access to locking screw

Tighten locking screw

Carefully position main assembly unit back into position

Carefully move mechanism into place

Tighten rotor shaft cam hex nut

Place new seals into position – note make sure top seal is the right side up as marked

Place flush ball ring back into position (the white ring in photo)

Remove main assembly – note 7/16in deep well socket

Carefully lift head off mounts

Loosen the two screws holding head to base

Job finally complete and happy to report the M-Series only cycles now when the heads are flushed!

I am happy to report that the heads are all done and working perfectly. I am equally happy to report that Lance was around to give me a hand as there are times when two sets of hands are required. The first head took us around an hour to complete but with each head we became faster and faster. The last head was done in record time of 16 minutes from start to finish and that includes stopping to take these happy snaps.

Bottom line, if your vacuum pump is cycling too much and you have tried the usual duck bill replacement strategy then the fact is it’s time to change your seals and flush ball. You will be glad you did!

Stay safe


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