Blakes Lavac - will pump out, but not draw in sea water

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aidancoughlan

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We've just launched 2 weeks ago, and noticed that our Lavac (working well since install 2 years ago) is not drawing in fresh sea water for flushing, though the pump seems to be working ok - I took it apart and cleaned out limescale in the pump just in case, and it is pumping out water from the bowl (lid up) ok.

However, when pumping out with the lid closed (sealed), the vacum is supposed to suck up fresh seawater to fill & rinse the bowl & outlet pipes - this it will not do.

Checking the Blakes website/manual suggests the following:

(1) Inlet seacock closed: Open inlet seacock and check that the outlet seacock is open as well.

(2) Failure of vaccum: When the seat and lid are closed and the
pump operated, the bowl should be sealed for around 30 seconds, i.e. you cannot lift the lid. Anything less indicates excess air bleeding into the system. Check the condition of the seat and lid seals.
Are all the hose clips tight? Check air bleed plug is in place and that
the hole is not too large.

(3) Inlet hose looped greater than 5 feet (1.5m) above water line.
In this instance it may be necessary to fit a non-return valve in the inlet hose just above the water line. This maintains a head of water to facilitate the initial syphoning of flushing water.

(4) Inlet pipe or seacock inlet outside the boat blocked:
In this condition the bowl will seal. Check seacock by closing it, removing the hose and then turning on. Check inlet hose for blockage.

It's not (1) above - the (blakes) seacock is in the open position (unless its possible for this to have failed in some way ?
It's not (2) above, it pumps out ok, and the seal seems solid (cant lift the lid for a minute or two)
Its not (3) above, the hose doesnt loop that high - and it was working the last 2 seasons.

So... if the seacock is blocked, whats it likely to be blocked with, and what's the best remedy? I've seen previous posts on search talking about divers, or taking off the hose and poking it clear from inside the boat (with water gushing in?). The access is very restricted, so I'm reluctant to remove the hose from the seacock unless absolutely necessary - Is there any short cut I can try before getting to this?
 
Possible something blocking the cone of the seacock, or a blockage in the pipe. Easiest way to check is to remove pipe from the loo and bend it below the water line while you open the seacock. If no water comes out you have a blockage. If water does come out you can lft the hose quick to stop it while you turn the seacock off. No further suggestions if water runs freely. If blocked however a flexible rod down the pipe and through the seacock could shift it.

Hope this helps.
 
Hi as you say the seat cannot be lifted for a minute or two the problem must be in the inlet pipe or the inlet seacock/skin fitting.
A couple of years ago my seacock handle parted from the ball inside the valve and it looked just like it was turned on but was actually off.
Can you use a inflatable dinghy pump to pump back down the inlet pipe from the toilet and see if any bubbles come from under the boat ? watch you don't blow out the air admitance button in the top of the inlet loop.
pete
 
Thanks guys, I'll try removing the hose from the loo first and bending it below the waterline to see if water comes in (a lot easier than removing from the seacock). I have an electrical "fish wire" which I think could poke down the pipe ok to try clear it.

I don't have a dinghy pump, but might be able to use a garden hose down the inlet hose to blow manually - I'll try the wire first to see if it frees anything.

Thanks for the suggestions, I need to get it sorted before next weekend, so they're most welcome.
 
Bet its the non return valve in the pump. Always has been with those symptoms on my boat for the last 10 years..... Even when cleaned, the flap valve is prone to distortion. Stick a new one in and hey presto!!!
Hope this saves you a bit of messing about.
 
There should be a strainer on the inlet seacock. It easily gets bunged up with bits and pieces of shell all cemented in place with a few good coats of antifoul. If you did not poke all the holes clear when you antifouled then theres a good chance thats the problem if you do not find anything in the hose.


If it pumps out with the lid up and creates enough vacuum to hold the lid down firmly for a couple of minutes its not the pump.

Can you hear it sucking air in via the bleed hole in the inlet pipe?
If you can then the blockage is at the seacock end.
If you can't then the blockage is at the loo end or the vent is blocked too.
 
[ QUOTE ]
inlet seacock. It easily gets bunged up with bits and pieces of shell all cemented in place with a few good coats of antifoul. If you did not poke all the holes clear when you antifouled then theres a good chance thats the problem

[/ QUOTE ]
That's a distinct possibility - I didnt anti-foul myself this year (I had some inexperienced crew helping me), and I didn't check the seacock strainers either. I did notice there was a calcified thingy stopping the speedo paddle wheel working - maybe they've taken residence in the water intake too.


[ QUOTE ]
Bet its the non return valve in the pump....... Sorry, not only that but the pumps are made near you and they have a totally excellent customer services section

[/ QUOTE ]
I don't think it's the pump - it seems to be sealing the vacum, and pumping out ok. - I did take it apart for a look though, and it cleaned it out (surprised at the calcified deposits after a couple of years).

[ QUOTE ]
Can you hear it sucking air in via the bleed hole in the inlet pipe?
If you can then the blockage is at the seacock end.

[/ QUOTE ] ... Yes, the vacum seals ok, and for a minute or two while it slowly clears I can hear the air hissing into the vent - putting a finger on it stops the noise. Sounds like this confirms that it is the water intake that is blocked. The end of the pipe at the pump is clear, so I presume its most likely the seacock.


Thanks for the suggestsions, I'm going to try bending the pipe below the waterline, fiddling with wire to poke through. If that doesnt work, off with the hose (which I think will be difficult) and poke directly in the seacock. Failing that - lift out !
 
not the most pleasant of suggestions ! But I is it possible to reach the inlets from a dinghy. Certainly on my boat I can poke a screw driver up to check for blockages.

Alternatively can you blow air back down the pipe successfully ?
 
Shut sea cock remove pipe end from toilet, raise above water level,fill with water to top,open sea cock and watch how quickly it drains down, or lower wlole pie BELOW sea level and open sea cock should have full bore coming out.. Saves drying out to inspect.
 
Was down the boat this evening.... I got the hose off the seacock (easier than I thought), and no water ! I poked around a bit with a screwdriver, and got blue smelly gunge on the end of it - smells like paint, and I think it is. I reckon that SWMBO and the sister overdid the antifoul when they did it, and clogged up the water strainer.
I will probably have to lift out to check it out.

In the meantime (overnight) I put some Glyns Tar Remover (safe on grp, but I hope the boat is floating tomorrow) down the seacock to see if it would soften, and remove the paint - I will try tomorrow evening and lift out if not.

Many thanks all for the suggestions.
 
A lift out seems drastic. Can't you dry out alongside somewhere, scrubbing piles perhaps. Presumably not a twin keeler.
 
we had a small fish in the tube once. It blocked the sea water outlet in the bowl, kep vacuum intact for a long tiome obviously but prevented most seawarter to get into the bowl. try and blow your inlet system with an air pump to get everything out and try again..
Good luck
can't be anything serious because the Lavac is a superior system with very little parts that can break
cheers
 
[ QUOTE ]
A lift out seems drastic. Can't you dry out alongside somewhere, scrubbing piles perhaps. Presumably not a twin keeler

[/ QUOTE ]
Well, not conveniently before we go cruising.... there is a drying post at a marina about 2-3 hours away .

[ QUOTE ]
try and blow your inlet system with an air pump to get everything out and try again..

[/ QUOTE ] That's just what my (non-boaty) dad suggested ... sounds like a plan, but couldnt get hold of an air pump at short notice.

I did haul out this evening (out of hours, for a small consideration at one of the local clubs)... picked at the small grill holes with BBQ skewers, and hey presto.... lavac is flushing again. Hopefully it remains clear (I suspect there may still be some paint residue inside, but hopefully it will dissolve rather than congeal again).

Thanks for all the reponses.
 
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