Lavac and volume of intake flush water

[FairweatherDave]

Just replaced our Lavac Zenith with a Lavac Popular. (Hinge lid broke on the Zenith and I was ready for that with a Popular I got second hand here).
Was getting some backflow from the pump and decided to fit the service kit for the pump. The old joker valve was the culprit and the whole job was worth doing.
However this has not solved the other problem which is a lack of water refilling the bowl. If I tip a bucketful in the pump clears it beautifully. The vacuum on the seat lid lasts a while but is not as powerful as the suction on the Zenith. The instructions say sealed for 30 seconds after the second pump cycle, unfortunately ran out of time to test that today. There is a vent hole on the inlet pipe which has not been making the characteristic hiss. I have poked it. However a bigger hole would surely reduce the amount of water drawn in.
I disconnected the intake hose at the seacock end and blew hard down it, there did not feel like there was any resistance. I opened the seacock briefly and there was a modest flow into the boat, poked around with a screwdriver while open but not much changed.
My conclusion is air is getting into the system but where to look? The lid and seat seals are pretty much new and do create suction for a while. Any pointers? Or am I barking up the wrong tree?

Alternatively as the Popular is a smaller cistern it is not going to exert such suction, and it is designed to use less water. But we need more than we are getting at the moment.
Hope to get some replies. I hate being halfway through the job. Want to head back asap and experiment but a bit of input here could be really helpful. Cheers Dave

 

[VicS]

Just replaced our Lavac Zenith with a Lavac Popular. (Hinge lid broke on the Zenith and I was ready for that with a Popular I got second hand here).
Was getting some backflow from the pump and decided to fit the service kit for the pump. The old joker valve was the culprit and the whole job was worth doing.
However this has not solved the other problem which is a lack of water refilling the bowl. If I tip a bucketful in the pump clears it beautifully. The vacuum on the seat lid lasts a while but is not as powerful as the suction on the Zenith. The instructions say sealed for 30 seconds after the second pump cycle, unfortunately ran out of time to test that today. There is a vent hole on the inlet pipe which has not been making the characteristic hiss. I have poked it. However a bigger hole would surely reduce the amount of water drawn in.
I disconnected the intake hose at the seacock end and blew hard down it, there did not feel like there was any resistance. I opened the seacock briefly and there was a modest flow into the boat, poked around with a screwdriver while open but not much changed.
My conclusion is air is getting into the system but where to look? The lid and seat seals are pretty much new and do create suction for a while. Any pointers? Or am I barking up the wrong tree?

Alternatively as the Popular is a smaller cistern it is not going to exert such suction, and it is designed to use less water. But we need more than we are getting at the moment.
Hope to get some replies. I hate being halfway through the job. Want to head back asap and experiment but a bit of input here could be really helpful. Cheers Dave

You are probably on the right track looking for air leaks. Lid and seat seals are the obvious first to look at, but these are new so should be OK. Hose joints with the pan and the pump suction may be others but will almost certainly weep some water when standing if not tight.

Maybe the pump is not performing as well as you think ????

Possibly the water inlet is restricted. Is there a strainer on the outside? They get blocked up with antifoul if nothing else. Maybe the inlet hose is restricted ... blowing though it is not much of a test

Maybe you have enlarged the vent hole too much ......... normally two sizes are supplied and the one which leaves the right amount of water in the bowl is the one to use. The smaller hole leaves more water. the larger one less water as you realise.

 

[FairweatherDave]

Thanks for that Vic, I was hoping you'd take a look.
The liklihood is my installation of the "new" toilet is not quite correct yet.
Then either my second hand goods are not as good as I thought. Or the change in volume from the Zenith to the Popular has some bearing.
First step the 30 second test for suction. Wrap some insulation tape around the inlet vent.
Then redo the inlet spigot. Plus check the seat and lid seals. Do another 30 second test.
Go snorkelling and poke the inlet a bit more.
At least the pump empties the bowl.

 

[alan_d]

The liklihood is my installation of the "new" toilet is not quite correct yet.
Then either my second hand goods are not as good as I thought. Or the change in volume from the Zenith to the Popular has some bearing.

Last year I replaced my Zenith with a Popular, and once I overcame the problems of getting the pan-to-hose connections to seal properly it has worked faultlessly, so I don't think it is the change in volume.

 

[FairweatherDave]

Thanks Alan. That's good to know.

 

[Besonders]

I have a lavac popular and experienced similar problems. My issue was the antisyphon loop and valve. inside the adjustment valve is a minature joker valve which had clogged with salt, keeping the lips from closing and allowing excessive air into the system. a clean with hot soapy water solved the issue. Apologies if you have already tried this or your system is not the same

 

[FairweatherDave]

Thanks Besonders. My "hole" in the anti-syphon loop was and is a simple drilled out not much thicker than a pin hole. Maybe a fat drawing pin hole size.
However I returned to the boat today and pretty much instantly spotted the problem. The sealing ring on the lid had been disturbed. My suction test only maintained negative pressure for 20 seconds. However setting the seal right still did not draw enough water into the bowl, so I taped over the anti-syphon hole and hey presto loads of suction and an appropriate volume of water in the bowl. One over happy FairweatherDave .......

 

[VicS]

I have a lavac popular and experienced similar problems. My issue was the antisyphon loop and valve. inside the adjustment valve is a minature joker valve which had clogged with salt, keeping the lips from closing and allowing excessive air into the system. a clean with hot soapy water solved the issue. Apologies if you have already tried this or your system is not the same

An anti-siphon loop and valve is unusual for a Lavac unless this is some recent innovation. They have loops but usually just the pin hole vent in the inlet pipe which as been referred to already.

A Lavac as I know them would not work with a normal type of antisiphon valve in the inlet pipe.... it would just suck in air and no water

 

[Besonders]

An anti-siphon loop and valve is unusual for a Lavac unless this is some recent innovation. They have loops but usually just the pin hole vent in the inlet pipe which as been referred to already.

A Lavac as I know them would not work with a normal type of antisiphon valve in the inlet pipe.... it would just suck in air and no water

VicS,
thats how mine came with the boat when i bought it 6yrs ago (24yr old Dromor, 1 owner from new not charter) I thought they were all like that, Must have been the previous owners modification. Still i can confirm it works perfectly and i can with some fiddling adjust the amount of water entering the bowl, i do have to remove and clean the valve each season. ..Thanks for the info

 

[VicS]

Thanks Besonders. My "hole" in the anti-syphon loop was and is a simple drilled out not much thicker than a pin hole. Maybe a fat drawing pin hole size.
However I returned to the boat today and pretty much instantly spotted the problem. The sealing ring on the lid had been disturbed. My suction test only maintained negative pressure for 20 seconds. However setting the seal right still did not draw enough water into the bowl, so I taped over the anti-syphon hole and hey presto loads of suction and an appropriate volume of water in the bowl. One over happy FairweatherDave .......

It still does not sound right. If the "pin hole" is sealed off completely no air will get in to break the siphon and water will cotnue to flow in if the toilet is below the waterline until you shut the seacock, it will be ages before you can open the lid, and the bowl wll be full of water when you do. Air must, therefore, still be getting in somewhere , lid / seat seals or hose connection on the pan. Difficult we found to get old hose to seal properly on a new toilet .

VicS,
thats how mine came with the boat when i bought it 6yrs ago (24yr old Dromor, 1 owner from new not charter) I thought they were all like that, Must have been the previous owners modification. Still i can confirm it works perfectly and i can with some fiddling adjust the amount of water entering the bowl, i do have to remove and clean the valve each season. ..Thanks for the info

Very strange.

It should work without any fiddling with just the pinhole vent in the inlet hose. Maybe just need an very infrequent poke if it begins to take too long for the vacuum to decay or if there is too much water left in the bowl


Instructions for the Lavac toilets on the BLT website at http://www.blakes-lavac-taylors.co.uk/pdf/lavac.pdf
( a bit out of date though regarding the models and the type of electric pumps fitted nowadays)

 

[FairweatherDave]

Point taken Vic. I will be monitoring the level but unlike your friend with his Westerly, I do close seacocks underway, or at least when we leave the boat. Nothing is obviously weeping either. Got to say, I love the simple design of the Lavac. And a pan of clean water makes me very happy!

 

[yerffoeg]

We have had a Lavac Popular on our boat for the past 15 years and have learnt to live with its foibles.

First try replacing the two seals for the lid and seat.

If that does not work, then you will need to bite the bullet and do the job that I did recently and every 5-10 years - take the Taylors pump apart and replace the main diaphragm and valves ( the replacement kit is not cheap).

We had the very same problem of inadequate filling of the bowl. Replacing the main pump diaphragm, which had become hardened and perished, corrected the problem.

Incidentally I think the deterioration of the internal rubber pump fittings was accelerated by putting vinegar down the toilet, which is often recommended to reduce crystalline build up. I have now stopped that practice and instead over-flush instead.

 

[differentroads]

I had the OP's problem six months ago. I had to replace my 40 year old bowl with a new Popular model (dropped the handle onto the seat hinge flange, the ceramic sheared off!)
Took ages to stop it backfilling. Six months earlier I'd replaced the pump, the valve diaphragm, etc, all the hoses and even the hose clips. The only thing i hadn't changed was the antisiphon vent (sticky tape and a pin hole rather than the pukka rubber valve).
After days of fruitless changes of sticky tape and pin hole sizes, I gave in a bought the proper valve. And while I was fitting it, noticed that every hose clip was half a turn loose, so I retightened them. One or both of those actions fixed the problem. I suspect the loose clips were allowing air in after flushing, although I couldn't detect a problem by ear or eye. Sticky tape and pin holes had served me fine for six years, though the proper valve leaves less water in the pan to slosh about under way.
I'd replumbed the galley, bilge pumps and engine in the last two years. This experience set me to rechecking all my hoses and I found a lot of slightly loose hose clips despite having originally cinched them up tight with a little t bar nut spinner.