Lavac suction problem

[Parmesan]

Over the winter, I replaced the hoses on my (manual) Lavac and serviced the pump with the service kit. I also replaced the L shaped spigot on the back of the bowl.

On going back in the water, however, the heads don't work. I can hear air bubbles being pumped out below the boat, but fresh water isn't being sucked into the bowl.

I have covered the vent hole (temporarily) with amalgamating tape (in case it was too big) but this didn't fix it. Also if I remove the hose from the spigot, put my hand over and pump, I don't feel a suction. The seat lid appears to be sitting correctly but I'll recheck that. Hose clips appear tight.

I am assuming it is an air leak (leaking in), but there isn't any obvious source. I used the thick white rubber sanitation hose so would be a bit surprised if it had a hole all the way through.

Are there any other suggestions for things to investigate or try to narrow down the cause? Also, could there be any problem with the pump (misassembly, over or undertightening) that would cause this problem but still allow it to pump air out?

 

[Boathook]

From your comments there is a problem with the seals somewhere allowing air in.

Lavacs are normally 'bullet' proof.

This can be confirmed by filling the bowl with water and pumping out with the lid open. The bowl should empty.

If it does empty shut the lid and pump out whilst listening for any hissing noises around the seat area. Also double check the L spigot on the back of the bowl. It should have a rubber seal on it.

 

[rogerthebodger]

I had a simular issue some time ago and i would look at the l shaped connection at the water suction at the back of the lavac. If its the outlet hose or connection water would be leaking out.

The other issue I had was the seal on the seat that causes a loss of suction if the seat was not pressed down fully. A replacement of the seat sel fixed my issue

 

[srm]

How old is the Lavac? Very old ones had an alloy bowl powder coated, once the coating got damage the alloy corroded underneath it giving an uneven surface. If not too bad pressing the seat/lid down firmly while pumping would solve the problem.

If a ceramic bowl I find it surprising that you have this problem. I fitted a new one to my last boat. On selling the boat 15 years later it was still working as it should with the original seals and pump parts, and this included daily use for 6 months plus per year for at least ten of those years. Check that you have fitted the seat and lid seals correctly, you could also try pressing down on the seat while pumping as an initial test. If these are OK then the spigot at the back could be suspect, was it fitted correctly and has a secure seal or was it dislodged while fitting the inlet pipe?

Moving down the list of probabilities, how did you fit the hoses? Were they heated and kept soft while tightening the clips? Hot air guns are popular on the forum for fitting reinforced hoses. I used a domestic steam cleaner with a jet nozzle. Dipping the end in a pan of boiling water never worked for me, the hose would cool and go rigid before I got it on the connector.

 

[rogerthebodger]

Have a look at this link to identify which Lavac you have

Lavac Spare Parts Drawings

Mine is a zenith but the base is not a separate plastic base id combined in the ceramic bowl

Note how the suction inlet is fitted

 

[alahol2]

Agree with Boathook. Fill and pump out with the seat up. If it empties then the pump is almost cerainly OK and you need to check the seals.

 

[rogerthebodger]

. I can hear air bubbles being pumped out below the boat, but fresh water isn't being sucked into the bowl.

that would cause this problem but still allow it to pump air out?

The only cause would be an air leak into the pump, but I would look at the seat seal or the water inlet connector

 

[PetiteFleur]

This is what happened to me last Monday after I had also replaced all hoses and refurbished the pump. I had to fill the bowl with water, closed the lid and it worked as normal. I did only did this once though, so will check again this weekend.

 

[srm]

This is what happened to me last Monday after I had also replaced all hoses and refurbished the pump. I had to fill the bowl with water, closed the lid and it worked as normal. I did only did this once though, so will check again this weekend.

Never had that problem with my Lavacs. However, you have reminded me of the charter yacht I went on having finished my degree. Did not notice what type of WC as it was as only the second cruising yacht I had spent time on, but do remember the skipper filling the bowl to the brim via buckets to prime it then pumping it out.

 

[KevinV]

If it's the same pump as one I've recently fixed it's possible to fit the inlet flap valve backwards.
With dry pipes I had to prime the pump with a bucket of water and the lid open - sucking water with an air vacuum is a lot to ask.