problem with lavac

[dolphin]

understand the point but this problem is not present, when pumping out only the liquid - the lid is completely dry

looking at the lavac user manual, the system is more close to one suggested on page 20 fig.1 - 4. Ball check valve or vented loop

It should have an air bleed situated at the highest point in the loop in the inlet hose. Its purpose is to break the syphon and allow air to enter so that you can open the lid reasonably soon after use. The size of the vent hole (2 of different sizes are usually supplied) determines the volume of water left in the bowl. Lack of this vent is probably contributing to your problem as the retained vacuum is probably reducing the effectiveness of the flush and sucking excrement lodged in the pump back into the bowl with sufficient vigour to foul the underside of the lid.

See the Lavac user manual .... http://www.blakes-lavac-taylors.co.uk/pdf/lavac.pdf

 

[Billjratt]

I have a Lavac.
I think you may have a blockage in the INLET hose or fitting, causing a vacuum which draws the soil back into the bowl easier than drawing flush water from the sea.
The vacuum can be strong (and you do say it takes a long while to open the lid) enough to invert the joker valve which will get flipped back to normal next time the loo is used. Surely you can feel the pump resistance abnormally high? - compare with the lid open then closed -water only.

 

[dolphin]

thanks a lot for all the replies and advises
will check for the possible inlet blockage and will try with slow strokes on the pump
with best regards

 

[VicS]

understand the point but this problem is not present, when pumping out only the liquid - the lid is completely dry

looking at the lavac user manual, the system is more close to one suggested on page 20 fig.1 - 4. Ball check valve or vented loop

You did not say it was a used with a holding tank but even so I dont understand the installation without an air bleed. Although you can stop the syphon by closing the inlet valve there is nothing to break the vacuum except for waiting until it has stopped drawing in water before closing the valve. This means you will then have a relatively large volume of water in the bowl when operations cease.

If its a simple pump out to waste system plumb it as shown page 15! I'd use a vented inlet loop like that on page 15 even with a holding tank. Its fundamental to the way the Lavac functions.

 

[dolphin]

there is no holding tank - it is direct overboard !
just like to clarify, how the system is build - inlet, valve, bowl, pump, overboard (the bowl and the pump are higher then the sea level)
once the pumping is stop, the valve is closed but even if it is not closed, the remaining water in the bowl is about 10-15 cm

You did not say it was a used with a holding tank but even so I dont understand the installation without an air bleed. Although you can stop the syphon by closing the inlet valve there is nothing to break the vacuum except for waiting until it has stopped drawing in water before closing the valve. This means you will then have a relatively large volume of water in the bowl when operations cease.

If its a simple pump out to waste system plumb it as shown page 15! I'd use a vented inlet loop like that on page 15 even with a holding tank. Its fundamental to the way the Lavac functions.

 

[pvb]

there is no holding tank - it is direct overboard !
just like to clarify, how the system is build - inlet, valve, bowl, pump, overboard (the bowl and the pump are higher then the sea level)
once the pumping is stop, the valve is closed but even if it is not closed, the remaining water in the bowl is about 10-15 cm

So, do you have an air bleed valve or not? It sounds as if it needs one, as the residual water level is rather higher than ideal.

 

[dolphin]

So, do you have an air bleed valve or not? It sounds as if it needs one, as the residual water level is rather higher than ideal.

NO, there is not an air bleed valve ! (this design in on the boat almost 40 years)
next time i go to the boat, will measure exact the residual water level before / after pumping with open/close lid as for the moment all the measures are about

 

[pvb]

once the pumping is stop, the valve is closed ...

Do you mean immediately after stopping pumping? Unless you wait for all the vacuum to be dispersed, closing the inlet valve can only result in waste being sucked back out of the pump.

 

[pvb]

NO, there is not an air bleed valve ! (this design in on the boat almost 40 years)

Regardless of the age of the installation, as far as I can recall Lavacs have always needed an air bleed valve, so it would be a good idea to have one.

 

[sailorman]

Regardless of the age of the installation, as far as I can recall Lavacs have always needed an air bleed valve, so it would be a good idea to have one.

correct & the larger the hole dia the lower the water in the pan.
some folk used to use the end cap of a Bic pen in place of the one provided

 

[VicS]

NO, there is not an air bleed valve ! (this design in on the boat almost 40 years)
next time i go to the boat, will measure exact the residual water level before / after pumping with open/close lid as for the moment all the measures are about

You sure there is no air bleed. Its only recently Lavac have included the diagrams you refer to in there manual. 40 years ago it would definitely only have shown the earlier diagram with a vent. I thinks it's necessary even with the holding tank ... just omitted from the diagrams ... otherwise there is no way of breaking the vacuum other than by letting it suck water in until it stops sucking.

Maybe its been there all along and is now blocked.

 

[Billjratt]

I agree with post #28 it's another way of creating the scenario i was trying to describe.

 

[dolphin]

Do you mean immediately after stopping pumping? Unless you wait for all the vacuum to be dispersed, closing the inlet valve can only result in waste being sucked back out of the pump.

this can be the reason but what i didn't understood why this not happened with the liquid and the inside of the lid is dry !
on the next visit of the boat will try to pump out without closing the inlet valve

 

[sailorman]

this can be the reason but what i didn't understood why this not happened with the liquid and the inside of the lid is dry !
on the next visit of the boat will try to pump out without closing the inlet valve

we never close any valves when on board

 

[dolphin]

You sure there is no air bleed. Its only recently Lavac have included the diagrams you refer to in there manual. 40 years ago it would definitely only have shown the earlier diagram with a vent. I thinks it's necessary even with the holding tank ... just omitted from the diagrams ... otherwise there is no way of breaking the vacuum other than by letting it suck water in until it stops sucking.
Maybe its been there all along and is now blocked.

yes, i am sure that there is no an air bleed as the intake hose is run on the bottom of the boat without loop and only with valve, which is all the time closed and open only once the loo is used

 

[pvb]

we never close any valves when on board

I never close any valves, any time.

 

[sailorman]

yes, i am sure that there is no an air bleed as the intake hose is run on the bottom of the boat without loop and only with valve, which is all the time closed and open only once the loo is used

the inlet should be looped as well as the outlet

 

[dolphin]

we never close any valves when on board

the inlet valve for the loo is always closed when not in use as there is no an air vent

 

[pvb]

the inlet valve for the loo is always closed when not in use as there is no an air vent

???

 

[sailorman]

the inlet valve for the loo is always closed when not in use as there is no an air vent

so loop it above the water line & add a vent then leave it on