Jabsco twist and lock issue sorted. Need a screw!

[pcatterall]

We had an ongoing issue with the twist and lock on our Jabsco toilet. I changed/cleaned the rubber flap valve thingy many times.
I realise, now that it was not the valve itself that leaked but due to one of the 4 screws that hold the pump to the base being ineffective.
The screw does not bite into anything and as a consequence after a bit of use water can seep around where the valve seats into the base.
3 screws seem to be holding it ok at the moment but I would like to get a fourth one in! The first few threads seem to have stripped in the 'plastic' base although there are threads
further down the hole. Possibly a longer screw would find purchase on these threads. If that fails I am not sure of what the best solution would be,. Possibly I could drill right through the base and screw to the timber below
( would this leak?) fill the hole with epoxy and drill out and fix a new screw ? what tap would be suitable for these type of screws?
I attach a pic of the screw, does this kind of thread have a name? would it 'self' tap if a suitable hole was drilled?
Your usual good advice appreciated as always.

 

[Tranona]

It is not a screw in the conventional sense, more like a machine screw and has stripped the thread because it was not put in properly. You need to get the screw located in the thread before you turn it. Otherwise you cut a new "thread" which strips the proper one and you will never get it to hold properly again. You might find a selftapper that goes further into the plastic but suspect that the original thread stops when the screw is tight. You might try epoxy but suspect it will not stick to the plastic. Otherwise something like CT1 may hold it in place long enough to stop the leak.

 

[CJ13]

Try a cut down ‘rawl plug’ cut down cable tie or even a match to pack out the hole. Don’t ask how I know this works!

 

[NormanS]

When reinserting any self-tapper it is always a good policy to turn the screw backwards until a "click" is felt. This helps to ensure that the screw goes into the existing thread, and doesn't try to cut another thread.
What I have done in this particular problem, was to tap the hole in the base to 8mm, drill out the hole in the base flange of the pump, and form a suitable stud from 8mm threaded rod.

 

[LadyInBed]

I drilled through and used nuts and bolts.

 

[Frank Holden]

I drilled through and used nuts and bolts.

Ditto

 

[billyfish]

Ditto

 

[NormanS]

All these people (above), including myself, who have had to modify the mounting of the pump onto its base, shows that the design is poor.

 

[Daydream believer]

All these people (above), including myself, who have had to modify the mounting of the pump onto its base, shows that the design is poor.

4 people out of hundreds
I have had mine apart quite a few times in 20 years & never found a problem. Handy to know that there is a solution though. Of course I may just be lucky. But they say that you make your own luck

 

[Momac]

A complete new toilet might cure the fault

 

[jwilson]

Or a new base unit - about £25....

 

[rogerthebodger]

You could also cut the manual pump off and replace t with an electric diaphragm pump and an electric flush water pump I I hve done with my Jabsco

 

[lustyd]

All these people (above), including myself, who have had to modify the mounting of the pump onto its base, shows that the design is poor.

Or it shows that Jabsco designed it to be cheap to replace parts. These bits get quite manky and carrying replacements isn't too onerous or expensive. Given the longevity of the design, and the complete market dominance I'd suggest the design meets their design criteria. You may disagree with the criteria, but all evidence suggests you're wrong, not them.

 

[NormanS]

Or it shows that Jabsco designed it to be cheap to replace parts. These bits get quite manky and carrying replacements isn't too onerous or expensive. Given the longevity of the design, and the complete market dominance I'd suggest the design meets their design criteria. You may disagree with the criteria, but all evidence suggests you're wrong, not them.

Well, they may get manky on your boat, but they don't get manky on mine.
Like most, I carry spares for working parts, indeed many people carry a spare pump, and maintain by swapping the pumps. A design that has coarse thread self tappers into the base unit, can only lead to the occurrence of stripped threads in the base unit, as evidenced by comment on this thread. I'm not condemning Jabsco Toilets, I think they are excellent and reasonably priced, but from an engineering point of view, the design could be improved. I improved one of mine by fixing the pump onto studs, instead of self tappers.

 

[Tranona]

The point is that they are NOT self tappers, but are similar to conventional machine screws with the thread moulded into the housing. The correct way to install them is to turn anti clockwise until the blunt ended thread on the screw engages with the slot in the top of the moulded in thread, then screw in. If you don't do that and treat it as a self tapper then you will cut the moulded thread up and hey presto you can demonstrate all your ingenious ways of making good your mistake.

If you treat them properly they work fine. If you abuse them you can start a thread on PBO say what a lot of c**p a Jabsco is.

 

[vyv_cox]

I had some work done on a petrol engined chainsaw. The cover was attached with self tappers into fibreglass, some of which had been stripped (not by me). The man doing the work pushed strimmer nylon line into the holes and refitted the screws. Worked perfectly

 

[Martin_J]

What is different with these screws to a common self tapper is that looking closely they have two threads, one being much more pronounced than the other.

Jabsco seem to call this particular one a self tapper and although I'm not on board I seem to think I've got two lengths of that type of screw in the spares box .. maybe, maybe not.

It also doesn't show on the list of spares for the manual toilet because for those, it's only shown in the spares kits. The double height thread does look like the ones below though (but only in one length)

 

[Martin_J]

On the manual loo it's the same screw that's used into the collar around the joker valve .. #31, 6 off in the parts list.

 

[NormanS]

The point is that they are NOT self tappers, but are similar to conventional machine screws with the thread moulded into the housing. The correct way to install them is to turn anti clockwise until the blunt ended thread on the screw engages with the slot in the top of the moulded in thread, then screw in. If you don't do that and treat it as a self tapper then you will cut the moulded thread up and hey presto you can demonstrate all your ingenious ways of making good your mistake.

If you treat them properly they work fine. If you abuse them you can start a thread on PBO say what a lot of c**p a Jabsco is.

Well, Jabsco call these screws self tapping screws, but no doubt you know better.

 

[lustyd]

Well, they may get manky on your boat, but they don't get manky on mine.
Like most, I carry spares for working parts, indeed many people carry a spare pump, and maintain by swapping the pumps. A design that has coarse thread self tappers into the base unit, can only lead to the occurrence of stripped threads in the base unit, as evidenced by comment on this thread. I'm not condemning Jabsco Toilets, I think they are excellent and reasonably priced, but from an engineering point of view, the design could be improved. I improved one of mine by fixing the pump onto studs, instead of self tappers.

They get manky because it's a seawater flush not entirely sealed from the outlet side, it's not a lack of cleaning. Also, the plastic degrades over time in UV so will begin to yellow.
Again though, what you perceive to be engineering and design improvements go against the design principals they have in place. Any fool can engineer a CNC machined aluminium pump with set screws holding it together. It takes a real pro to create a design that's cheap, doesn't leak, widely available parts, and good enough to be bought by the mass market with some profit margin left. I don't think it's the perfect design, but given we don't see better designs that are even remotely as popular that should tell you all you need to know about whether the design can be improved while maintaining a business.