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Waste tank outlet modification.


John W

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We have a Chausson Flash S2 and although we are very pleased with it there is just one issue that we are trying to address. It has two under slung waste tanks which have a lever valve which deposits the grey water directly below the centrally positioned tank. This is fine for motorhome service points but a pain on limited facility sites. The solution appears simple – fit a tank elbow connector add a length of 22mm plastic pipe to the side and finish with an outlet tap.

 

Problem – In order to fit the tank connector one needs to get access to inside the waste tank. Well there is an inspection cap on the underside of the tank but do you think I can unscrew it, no. Do you have any answers to get the cap off? Alternatively, a hole could be bored into the tank and the tank connector could be cemented around its flange and when secured the piping and tap could be connected. Your thoughts on this would be appreciated with any advice on adhesives to use.

 

 

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I once fitted an outlet to a waste tank by making a metal collar to fit around the fitting's flange and after drilling a very tight fitting hole and threading the outlet into the lower side wall of the tank. Then screwing through the collar and fixing it all in place with stainless steel marine self tappers, using silicone to seal it.

 

Many adhesives will not adhere to many water tanks and even silicone is not enthusiastic about it but if held firmly in place you will probably get away with it - I did!

 

Using flexible hose, supported where necessary, and a tap fixed to the side skirt of the van in a place that will not hit the ground or get covered in wheel spray completed the job.

 

If the tap is too high when fixed it can be held in place by a 'Terry' type tool clip and unclipped to drain down rather than an ugly looking drop plate.

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I did something like this first time using domestic size waste pipe with an elbow fitting off the original outlet but this was a bit too low and got ripped off. Hence I am attempting to us 22mm overflow pipe with other fittings from ScrewFix but I am not able to unscrew the inspection plate. So unless somebody can advise on opening the inspection plate I have to bore a hole to accept the tank connector and cement it in.

 

Thanks for the info on silicon securing of the tank connector. Has anybody used one of the high grab adhesives?

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First of all you need to know what the tank is made of. If it's PVC you can cement it. If it's Polythene or Polypropylene you cannot. And I mean you cannot cement it with anything and certainly not Silicone, which has no mechanical strength and will not stick to the above materials to any worthwhile degree. You may be able to use a tank connector if the tank is flexible enough to wangle the flange through a suitable hole and then tighten up the nut with a gasket between it and tank.
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I have managed to fit plastic 3/4 inch bsp fittings into a grey tank by boring in effect a tapping size hole and screwing the fitting into the tank effectively cutting its own thread. A coating of epoxy adhesive on the thread helped to seal the joint and keep it in place stay and place.

 

Its not the sort of bond that can be relied on but did the job.

 

I take it the insection cap is plastic and either a screwed thread or bayonet fitting. If there is somewhere to get a purchase near the caps circumference with the end of a length of timber, a clout with a mallet on the other end end of the wood might move it. Another approach is to warm the immediate area of the tank to get a little expansion and immediately give it a clout as before. Don't overdo the heating, think hair drier rather than hot air gun and then only for a minute or so or the heat spreads into the cap ruining the differential expansion effect.

 

 

I fitted 1 1/4 inch size drain and ball type tap to the epoxy and ply grey tank I made for my present van and found it the prices for fittings at a local ground works ( underground drains etc) supplier quite reasonable.

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I once used a rubber sink plunger to connect a pipe to the original outlet.

 

I found a plunger of the right diameter in Homebase, removed the handle, made a hole through and connected a pipe to it. I then attached the remains of the plunger to the tank outlet with a large clip. worked well.

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John W - 2012-04-23 7:51 PM

 

Problem – In order to fit the tank connector one needs to get access to inside the waste tank. Well there is an inspection cap on the underside of the tank but do you think I can unscrew it, no. Do you have any answers to get the cap off? Alternatively, a hole could be bored into the tank and the tank connector could be cemented around its flange and when secured the piping and tap could be connected. Your thoughts on this would be appreciated with any advice on adhesives to use.

 

 

....patently, if you can get access to the appropriate point after removing the inspection cap, then a nut-in fitting of some kind is likely to be the best and most reliable.

 

What's the issue with removing the cap? Inability to get enough torgue leverage to move it?

 

If it is "proud" from the bottom of the tank, I would be inclined to try something like a strap wrench as a first option.

 

The only inspection cap I haven't been able to remove was on my last 'van, where it was recessed into the bottom of the tank, and the only leverage was via a raised "flange" across the inset middle of the cap (rather like a reversed screw slot). There was little scope for applying any force with hands alone, so I gave up on this, as I had no reason to remove it other than for an annual rinse-out.

 

I resolved, if I ever had to, to try a piece of wood with two offset raised blocks screwed to it to engage with either side of the "flange". I reckoned that a piece about 3ft long would allow sufficient leverage to unscrew the cap (and the bits used would have been "shed bits".

 

Such a solution could also be used for a raised, "knurled" cap as fitted to some tanks (if the "knurls" are long enough to provide some purchase).

 

(Effectively, the suggestion is to make a wooden key or spanner to size).

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John W..

If your waste tank is like the one on our Chausson(..which also has outlet in the centre of the van,with sliding shutter type valve),then you may find that the outlet does actually have is a short "stub" of a pipe..which is more than enough to clamp/clip a hose/pipe too(..on ours' this "stub" is tucked up inside slightly and is not visible when viewed from the side..)

 

I can't recall the dia' off hand(50-60mm OD?)..but I do know that the rubber hoses/elbows & clips that I had kept from the INSIDE of a old wachine machine that I binned,fitted spot on! ;-)

 

Although I didn't fit an elbow & pipe arrangement(..due to what I considered to be limited ground clearance in our case),I did just fit short vertical hose,so at least I count line it up with the waste point..

 

Failing that,have a look on pages 19 & 20 on here,as there may be something....

http://www.caktanks.com/files/cak_catalogue_2012/2012_CAK_Water%20Tanks.pdf

 

Edit:..Oops! Having just re-read your post(*properly* this time :$ ),it appears that your tank may differ from ours'..so feel free to ignore the bulk ,if not all,of my witterings....(lol)

 

Having said that, I would assume that some part of it *must* undo somewhere..?...and I wouldn't be just sticking fittings to it with "bungo", until I'd checked out every other avenue...

 

 

 

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John W - 2012-04-23 7:51 PM

 

...Problem – In order to fit the tank connector one needs to get access to inside the waste tank. Well there is an inspection cap on the underside of the tank but do you think I can unscrew it, no. Do you have any answers to get the cap off? Alternatively, a hole could be bored into the tank and the tank connector could be cemented around its flange and when secured the piping and tap could be connected. Your thoughts on this would be appreciated with any advice on adhesives to use.

 

 

Robin Hood has pretty much covered this, but I can confirm that a home-made 'spanner' should work.

 

My Hobby's freshwater-tank has a threaded inspection cap in its top and the waste-water tank has two similar caps in its bottom. Each cap is large diameter, recessed, with three finger-hold 'dents' in its upper surface.

 

When I bought the motorhome none of the caps could be removed by hand, so I made up a tool to do this. It's a crude ugly thing made from a piece of thickish plywood roughly in the shape of a smallish table-tennis bat. Three short sturdy dowels are glued into holes in the centre part of the bat's 'striking surface' in positions that line up with the dents in the inspection cap

 

The 'bat' is held firmly against the cap with the dowels in the dents and leverage applied via the bat's handle section. By "leverage" I mean a smart smack with a hammer if manual force fails to move the cap initially. As the caps are sealed with a substantial O-ring, there's no real requirement to have them done up enormously tightly to make them watertight. So, when the cap is to be replaced, there's no need to resort to the hammer treatment.

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Just a further thought, have you tried removing the blade valve from the tank outlet to see how it is attached to the tank? I'm assuming there will be some kind of spigot to which it fits. If so, could you not obtain a suitable length of flexible outlet tube and attach one end to the spigot and the other to the existing blade valve, and re-site the blade valve to a more suitable location?

 

CAK tanks have a number of varying reinforced flexible waste outlet tubes, to quite large diameters. Smooth internal bore aids clamping, and prevents odds and sods catching in the grooves of the internally convoluted variety. I did something similar on our van, although the move was less radical. The flexibles are clamped on to spigots with "Jubilee" clips (as was the original, shorter, flexible) and the flexible tubes can be pre-formed a bit with immersion in hot water, or a hair dryer, or even electric paint stripper (careful! :-)).

 

You'd in any case have to wangle some support for the re-sited valve, and probably some intermediate support for the flexible, depending on length, but if possible I think it may be preferable to using rigid pipe, especially if plastic. It is surprising what hits things under the van while travelling, and the flexibles are more resilient!

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Did similar to "pepe" jubilee clipped a short (prob 3") long rubber pipe to the stub of the outlet then we have a 2m ish length of convoluted waste pipe with a 2" push fit drain elbow on the end which pushes in very nicely to facilitate emptying into non drive over drains. I am sure yours will be the same tank as "pepe's" and ours so should work.

Not sure which bit of your post pepe re-read that got him thinking his / my idea wouldnt work :-S

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ips - 2012-04-24 12:07 PM

...Not sure which bit of your post pepe re-read that got him thinking his / my idea wouldnt work :-S

 

..the little stub on mine(and I assume yours' also)is SO obvious,that with all this talk of "having to gain access to the tank" and of the need to fashion tools inorder to "unscrew" stuff etc,I just assumed that the tank must be different somehow.... :-S

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Thanks Robin Hood & Derek Uzzell.

My recessed plate has three raised sections so I produced "the bat" spanner in wood and managed enough hand leverage to unscrew the plate - end of round one thanks to the forum.

I am waiting for the two plastic 22mm taps from Hong Kong before I start drilling holes in the tank. Thanks George for your idea. Now that I can get into the tanks with extended socket set I hope to do the job correctly after threading the elbow into the tank followed by the flange nut inside. Watch this space :-D

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The trouble with outlet pipes is they are always close to the bottom usually giving just space to get the keeper nut on but not enough to get a socket or ring spanner onto it. Sometimes its so tight its either an open ended spanner end on or a screwdriver jammed under neath to hold the keeper.

 

Its the sort of job to suit a double jointed gibbon with an eyball and LED under his fingernails.

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George Collings - 2012-04-24 8:16 PM

 

Its the sort of job to suit a double jointed gibbon with an eyball and LED under his fingernails.

 

..and if you haven't one of them to hand,try the tried and trusted, "Closing your eyes and looking away,whilst sticking your tongue out slightly method"... (lol)

 

(...why does that always seems to help..?!?? :-S (lol)

 

 

 

...or maybe it's just me? :$

 

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Well I drilled the tank to enable the tank connector to be threaded in with mastic around the thread then left it to cure off. Managed to get the underneath inspect hatch off with the fashioned wooden tool but could only get part of my arm in and could not get the locking nut near the connector, even with an extension on the socket . At this stage thought I would leave it as George had done but enter the "good lady from indoors" whose arms are of a more slender build and hey presto she did it!!. Secured 22mm plastic pipe having cut it to the required length and fitted the tap on the end. Job done.

 

Many thanks for all the contributions. I can now tackle the second waste tank with confidence.

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