Head Mistress required

deejames

deejames

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Got a Heads problem - know there's a mistress who specialises in this sort of thing, but all advice gratefully received.
Lavac Zenith - has worked perfectly for 20 years. Over the winter, I decided it was time to replace all the bits that might be a bit dodgy. So ........ new seacocks (Blakes - arm-and-a leg-rollsroyce jobbies) - new pump (Henderson 5 in a white disguise), new seals on seat and lid of Lavac (only bit of old installation remainaing) and new hose (odour-proof white at a zillion pounds a metre). Everything same as before with pin-hole vent at top of waste outlet pipe.
Result ......... water spurting out of pin-hole vent when I pump, and vacuum in the Lavac that's still there after 20 minutes (i.e. - twenty minutes after pumping heads, it is still impossible to open lid !!)
Can't think how either inlet or outlet seacock could be blocked, so what might be the problem .........
 
You rang? :)

"Lavac Zenith - has worked perfectly for 20 years. "

It may have still been working to some degree, but at greatly reduced efficiency...'cuz nothing could work perfectly for 20 years with -0- maintenance...so here's what I THINK your problem is:

New pump is a lot more "powerful" than the old one with a worn out diaphragm...your seat and lid are actually sealing again for the first time in ages. However, it shouldn't take anywhere near 20 minutes for it to release, so Since I can't look at your toilet to see what you may have done to the bowl seal to create that much vacuum, I think you need to have a chat with Blake about that and how to cure it.

The next part is easy:

"Everything same as before with pin-hole vent at top of waste outlet pipe.
Result ......... water spurting out of pin-hole vent when I pump..."

That's because there's no air valve in the "pin hole"--which, if you look inside it, I think you'll find is actually be a threaded nipple, not just a hole (at least it should be). That air valve only allows air INTO the line to break a siphon, nothing out...so will eliminate the squirting. It didn't happen till you replaced the pump because the old pump wasn't generating enough pressure to force water out the hole...the new pump does. Install an air valve in the loop, and it will quit squirting.

Another solution is a vent line on the nipple...but it's a BAD solution because, while it solves one problem, it creates another more dangerous one: the line is so small--only 1/4"--that it quickly becomes clogged with salt, sea water minerals and waste...turning the vented loop into UNvented one that no longer has any ability to function as a siphon break because the source of air to break the siphon is plugged.

Call Blake...buy an air valve...and I think your problems will be solved.
 
Re: You rang? :)

Thanks Peggie.
Not quite true to say "no maintenance" - have always looked after the heads as it is somewhere I don't want to have to try and repair at sea, in the dark, with a blunt screwdriver and a weak torch. When original Lavac was new, the "vent" was a small plastic plug with a hole in it, and it worked fine from the word "go". I don't disagree with any of your comments and will obviously take your advice and contact Blakes, but I am nevertheles quite surprised that there's a problem with what - to all intents and purposes - seems to be an identical set-up to what was there previously.
 
Re: You rang? :)

"Not quite true to say "no maintenance" - have always looked after the heads as it is somewhere I don't want to have to try and repair at sea, in the dark, with a blunt screwdriver and a weak torch."

If only every boat owner understood that maintenance at the dock prevents most repairs at sea! Still, 20 years is a long time for anything to last, even with some maintenance...'cuz salt and just plain wear take their toll on housings as well as rubber bits, resulting in less and less efficiency that isn't recognized because it happens so gradually.


"I am nevertheles quite surprised that there's a problem with what - to all intents and purposes - seems to be an identical set-up to what was there previously."

Something is different (obviously!). I'm hearing of similar problems--vacuum holding interminably--with new Lavacs, so I suspect it's the newer seals. But I don't want advise on what to do about it because some of the solutions I'm hearing about seem to me to cause more problems than they solve.

You said, "the "vent" was a small plastic plug with a hole in it..."

I THINK that small plastic plug was the air valve...that it's now missing, or has failed and requires replacing. 'Cuz it needs to be there to prevent the spurting from waste pushed through the line.
 
I replaced the seat seals on my Lavac Zeneath the other day and at the same time replaced the small diameter hose (the one that supplies water to the loo). I did not put the valve in the loop and pumped the loo as per Blakes instructions and like you had a vacuum that took more than 20 minutes to break. I eventually broke the vacuum by slacking off a jubilee clip and then fitted the missing valve in the loop, tightened up the jubilee clip and, after this, the Lavac worked perfectly. I think you need a new valve thinggy, a couple of years ago I telephoned Blakes for this valve and they sent me two in an envalope; be interesting to see if they still do this! Good luck.
 
/forums/images/graemlins/shocked.gif THE PIN HOLE IS IN THE WRONG PIPE

The little pin hole, and it should be in a little insert a bit like the little plugs in that cheap ball point pens used to have in their ends, must go in the INLET pipe , at the top of the loop.
 
[ QUOTE ]
/forums/images/graemlins/shocked.gif THE PIN HOLE IS IN THE WRONG PIPE The little pin hole, and it should be in a little insert a bit like the little plugs in that cheap ball point pens used to have in their ends, must go in the INLET pipe , at the top of the loop.

[/ QUOTE ]

Nope...if the toilet is below the waterline and discharges overboard, vented loops are needed in BOTH lines--inlet AND discharge. And air valves are required both.

The one in the inlet has to go between the pump and the bowl, not between the thru-hull and the pump.
 
Re: You rang? :)

Peggy

Just to say my bog is the sweetest in the north Atlantic since i followed your advice to fit a freshwater feed to the inlet

I'm sitting on it now with a wifi connection and a wonderful view. Bless you!
 
Re: You rang? :)

Glad to be of help!

Btw...what do y'all think of this a means of supplying fresh water to flush the toilet:

A gentleman on the MoBo forum who calls himself Wiggo said, "Flexi bladder tanks by Plastimo, mate, that's what you need. ABout £50 or so from Marine Superstore at Puerto Solente. If it splits in a year or two, it's only fresh water that ended up in the bilge. The only hassle is fitting the hose to fill it through, but it's worth the effort."

Which gave me this idea: what if you teed a line using a 3/4" y-valve into the head sink drain to fill it? I THINK fittings must be owner installed in Plastimo bladders...so instead of the usual 1.5" fill, use a 3/4", same as sink drain. Keep the y-valve turned to the through hull except when you need to fill the tank...turn the valve and run water down the sink when you do. The tank could then go just about anywhere you can find room for it and be able to run a fill line to the sink drain.

Whaddaya think--a dumb idea...or a plan?
 
WRONG WRONG WRONG!!!

Edit:- see the user manual Look at the diagrams on pages 13 and 15

The pin hole goes in the INLET hose.
THERE IS NO PUMP ON THE INLET SIDE OF A LAVAC; the pipe goes direct from the seacock to the toilet. The pump is in the outlet. Pumping creates a partial vacuum in the toilet, which is why the seat and lid have to make a perfect seal with the bowl, and flushing water is then drawn in. The pin hole is neccessary for two reasons, firstly to break the vacuum in a reasonable time and secondly to to break the siphon which would continue to flow into the bowl if it is below the waterline.

I have been using one of these for over 25 years!

Ours does not have a vented valve in the outlet either. I would guess that the top of the bowl is about level with the water line, perhaps a little below. The valves in the pump stop any back flow and the normal operating procedure pumps sufficient air into the discharge pipe to effectively break any siphon there.

The seacocks on the boat I sail have not been closed in nearly 30 years (Although the owner would now admit that to be a mistake as they cannot now be closed)


The size of the pin hole is critical. If it is too large the toilet will not flush properly and if it is too small or becomes blocked you cannot open the lid for ages and you end up with too much water left in the bowl. If a Lavac is installed correctly, seals replaced when necessary and pump overhauled from time to time it will operate with no problems for years and years. Just follow the operating instructings on the plaque that comes with it and walk away!
 
Hi Peggy. Greetings from Brisbane.

I agree with VicS, in the case of DeeJames' setup. I have a Lavac on the waterline with the air valve at the top of the water inlet and this works perfectly. I cannot see how the vacuum could be broken with the valve in the discharge line as air would have to pass back through the one way valve in the pump.

You say:

"The [air valve] in the inlet has to go between the pump and the bowl, not between the thru-hull and the pump."

I don't understand this. On the Lavac, the inlet runs direct from the thru-hull to the bowl. There is no pump on the inlet side.
 
Sorry...have 5 conversations on 3 sites going right now and forgot which toilet we were talking about. (My goodness--all those caps! You ARE an excitable sort, aren't you? /forums/images/graemlins/wink.gif )

From what you're saying, it does sound as if he's misplaced a vent ("pinhole"). However, if the toilet discharge is connected to a below waterline thru-hull, a vented loop in the head discharge line IS advised. That any individual vessel may have gotten away without it forever doesn't change that, it only means his luck hasn't run out...yet.
 
It's been the only bit of excitement in an otherwise miserable day.

The vision of some poor soul ending up with a toilet that was unusable and inclined to spray anyone who tried to use it with sewage after spending probably something like £400 was just too much, and all because of a pretty small mistake!

Sorry David
I hope you've found the time to look at the manual. I note that two sizes of vent are supplied, one for use in installations below the water line and the other for use above the waterline, both reqire a 1/8" hole to be drilled in the pipe.

There is absolutely no suggestion in the manual that a vent valve is needed in the outlet pipe in any conditions and Lavacs are sold for installation above or below the water line.

They have a reputation for reliable trouble free operation.
 
FWIW, I have installed a Lavac in Damarri and followed the instructions in as much as I have not put a vent in the outlet pipe. For the inlet, I felt that the "pin-hole plug" was a bit basic and likely to clog, I also had a mismatch between the size of the inlet hose (3/4") and the inlet seacock (1 1/4").

I solved the two problems with one solution by using a Vetus syphon breaker..... the type with a multi-size hose tail on both sides so I was able to come IN with 1 1/4" hose and then on to the loo with 3/4". The vent is way too large for the Lavac so I have run a short length of (I think 8mm) hose from the vent on the Vetus fitting to a convenient position and then partially blocked this hose with a not too tight fitting bolt. The "vent" is then achieved by the air bleeding down the thread of the bolt and is to some extent adjustable by varying how far you screw the bolt into the tube. At the moment I think the bolt I am using has too fine a thread as it takes several minutes for the vacuum to subside..... room for further refinement!

'Anyone know where I can get a 5/16" whitworth bolt? /forums/images/graemlins/wink.gif
 
Hi Peggy

Again, I have to side with VicS in his pointing out that the Lavac toilet system, with an air valve in the inlet line, does not also require an air valve in the discharge line, even with the bowl below the water line. I think your recommendation to have an air valve in the outlet line needs to be challenged because, while it may be relevant to other toilet installations, in a typical Lavac installation it could do more harm than good. Certainly, an air valve in the discharge line is not recommended by Blakes for any installation of their heads. In fact, a valve on the discharge side would bleed off some of the pump's thrust and could, conceivably, prevent the full discharge load from being dumped.

As far as I can see, the chance of syphoning back through the discharge side in a Lavac setup is very remote, since if the lid can be opened, the pressure in the bowl has equalised to atmospheric and thus the initial 'sucking' force to get the syphon started does not exist. We always wait after flushing and open the lid to ensure this is so (and then we always close both seacocks anyway). Two other things prevent discharge line syphoning: the one way valves in the pump, and the fact that the distance of the discharge piping from the top of the loop to the bowl is always less (in my experience, at least) than the distance from the top of the loop to the thru-hull, meaning the weight of water in the shorter distance (assuming it could flow back through the one way valves) cannot lift the weight of water in the longer to get the syhon started.

I am a regular reader of your USA column and I regret my first direct contact with you should involve a disagreement. I have put great store in your comments on getting lots of air to the holding tank (for which I use a wave-powered pendulum pump in addition to a 40 mm vent), and I am planning to follow your advice about teeing in a fresh water flush line for the inlet pipe, so I take this opportunity to thank you for this valuable and practical advice.
 
Paul, the beauty of the air vent in the Lavac system is that it is so basic yet effective. Although over a long period it may get partly blocked in the short term because it is sucking clean air inwards it stays clear. If and when it does start to get restricted you will know because time for the vaccum to be released will become extended and the volume of water left in the bowl will increase. Clearing it is so simple with a bit of fine wire. Even a little fresh water dribbled on it will quickly dissove any salt crystals.

To my mind you have gone from a simple, effective & reliable idea to a lash up, as that is how I see your bolt screwed into the end of a piece plastic tubing.

Regarding the seacocks Blakes supply two sizes, one to fit 19 mm pipe for the inlet and the other to fit 38 mm pipe for the outlet. The inlet seacock should also be fitted with a coarse screen on the outside (about 1/8" diameter holes)

Coming back to your bolt (or do you mean set screw?) I'm surprised you cannot find a 5/16 whit one (have you tried looking for 5/16 unc as that is almost identical)
Why not plug the end of the tube and fit one of the Lavac "pin holes" there.
 
[ QUOTE ]
the discharge piping from the top of the loop to the bowl is always less (in my experience, at least) than the distance from the top of the loop to the thru-hull, meaning the weight of water in the shorter distance (assuming it could flow back through the one way valves) cannot lift the weight of water in the longer to get the syhon started

[/ QUOTE ]
I think that this is either dangerously misleading, or just plain wrong. The siphon effect has nothing to do with the length of the pipes, and everything to do with the head of water. If you have a pipe full of water, one end is submerged, and the other end is lower than the water surface and at atmospheric pressure, then water will flow. It doesn't matter how long and convoluted the pipe is between the top of the tube, and the submerged end.

Sorry to be picky, but getting this wrong could have serious consequences.
 
Apologies

Hi Rich_F

You're quite right of course. I apologise, and to Peggy as well. I don't know what I was thinking. Well, perhaps I was misled in thinking of my own setup, where the base of my Lavac is just above the water line with the boat at rest.
 
Whos a silly boy then !!

In my haste to get everything done, and with a slightly "been there done that before" attitude, I put the bleed plug in the outlet rather than the inlet pipe.
So - it isn't surprising that it didn't work. Thanks for all the posts - if I had not read through them, I would have assumed that I had done the job exactly as before, and would still be tearing my hair (in the singular now - unfortunately) out !!
 
Re: Whos a silly boy then !!

B**** H*** - After reading all this I've put the 'pin hole' in the wrong pipe!! Just fitted a new Lavac & new hoses and I'm sure I put the 'vent plug' in the outlet pipe......... Have to check this weekend. Oh well - something else to sort as well as the engine, sails etc etc - perhaps I'll actually get a decent sail by the end of the season.
 
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