When I bought my 1985 Westerly Seahawk 'Magic Hawk' the heads was not a pleasant place to visit! There was a constant odour present (even after a thorough clean) and I found that the Henderson Mk V pump was leaking which was soaking into all sorts of things thus retaining the smell. Even the Blakes seacocks were seized in the open position therefore I decided to start from scratch and strip everything out. The seacocks had been badly maintained therefore I replaced them with new, together with the inlet and discharge pipes. I stripped the pump and replaced all of the seals and valves which were provided in the Henderson spares kit. I have also added a 38mm vented loop to the highest point of the discharge pipe to break the siphon action more easily. Currently, everything is working perfectly with no leaks and the odour has vanished, HOWEVER the only problem I now have is the toilet seat will not release due to the vacuum created when pumping. It should release after about 60 seconds according to the Lavac website, but you can wait six hours and it will still be stuck fast! My pumping sequence is 8 - 10 strokes of the handle, wait 5 seconds then a further 5 - 6 strokes which is as per the instructions on the Lavac notice behind the loo! After the final pump, I can hear the vented loop 'whistle' as it allows air to enter the discharge pipe so that is working okay. At present, I have to force the seat upwards to break the seal which reveals that the bowl is almost full of clean water. Clearly, there is no air passing back through the pump and into the toilet bowl to release the vacuum so does anyone know the vital piece of information that I'm missing please?

Just an observation which might be your problem-the flow via none  return valves thru toilet is from inlet seacock to inlet pump to toilet bowl to outllet.My conventional toilet syphoned from inlet into bowl. My toilet has a choice-you can empty bowl without sucking in any more water or flush thru with continual stream of water.If yours only dry empties as you suck water out of bowl and bowl is sealed down onto bowl rim and nothing is coming thru from inlet side you will create a very effective vacuum.

Would have thought there should be a fine breather hole similar to anti syphon  loop to allow air to very slowly re enter bowl?

Phil

Phil

Many thanks for your comments. The Lavac system has the pump on the discharge side with both inlet and discharge hoses looped-up to a point above the maximum heal angle of the boat. It will empty in both modes you describe above, so to pump out without sucking-in any water simply leave the seat or lid up and to create a flow of sea water, put the seat and lid down to engage the seals against the bowl. I can confirm that there is a strong flow of water when pumping through with the seat and lid down which is evident when I force the seat open again later and the bowl contains rather too much clean water.

I wouldn't disagree with your last comment about a breather hole to allow air to re-enter the bowl but from where? My local chandler suggested putting a vented loop at the highest point on the inlet side but surely this would stop the syphon action when pumping as it would simply suck in air through the valve instead of water up the hose? I don't particularly want to experiment by doing this unless it is the answer given that all my pipework is brand new and would require cutting to fit the loop!

Mark

Okay chaps - no need to go any further with this one as after more research, I think I've found the answer. As Phil suggested, there should be a breather hole in the inlet hose at it's highest point. I downloaded a document from www.Blakes-Lavac-Taylors.co.uk/prod03.htm  and found a diagram and the following on page 15:

Liz

Many thanks for the tip - anything to make life easier, especially for my 'other half' who is only 5' 1/2" tall and struggles to pump the loo as the handle is too high for her! I managed to obtain the recommended  bleed valve (as above) and found my £3 bought me what resembled two plugs from the end of a biro, one black the other white, with the black one having a slightly larger hole punched in it. I have tried them both and they do work; the black one leaving less water in the bowl as it lets in more air. Neither leaked which is the main thing so all is now well in the Seahawk heads!

Mark

I've just spent a couple of weeks on a yacht with 2 Lavac loos.

It takes an age to flush them and reuse them to then flush again.  You have to wipe the seat after flushing otherwise you get wet cheeks.

Why do people like them compared to a simple Jabsco which is far simpler to use and service and very inexpensive?

Well Scotty, it's because lots of people are too gung-ho when they pump the Lavac, ie overpump, which is how you achieve the wet cheeks effect.

I love our Lavac, as we don't have to remember to close any seacocks to avoid flooding, the anti-syphon does that for us.  I've had it to bits many times for cleaning and maintenance, and it is beautifully simple to understand.

Make the vent hole in the inlet pipe slightly bigger until you get the correct result!

Most sulphurous smells are due to decaying algae in the inlet pipe which does need cleaning occasionally.

Ps to the Jabsco guy...

The Lavac operation is much simpler and more robust.

I've had several pump type toilets and they ALL start to leak and stink the heads out. The Lavac is far superior.

White vinegar or sodium bicarbonate are great odour removers AND very cheep!!