blackwater tank intakes placement Q

[vas]

another (possibly) silly Q from me, but this got me v. confused. I'm about to secure the blackwater tank in place and routing pipes is just not right (to me at least!)

You see a pic of the 108lt black water tank (in blue ) with outlets on top (as expected) for both pump and deck outlet. Pipes have internal tubes coming to the bottom with slanted cuts, effectively enabling sucking up to the last 10-15mm. I'm happy with that (as I don't think I can have other options there...).

There's also a smallish outlet on top side (I assume) for the vent.
Next to the round inspection hatch is a DIN_whatever 5 stud blank for the level indicator.
All that's fine by me.

Now, how the hell is the liquids meant to get in the tank???
There are 4 (two visible in the bottom of the pic) blanked holes with threaded parts AT THE BLEEPING BOTTOM of the tank!
If I use them for the two toilets inlets, this means the nice white odour free, non-permeable, rather expensive, sanitary pipe I bought is going to have it's last foot or so full of **** almost all the time!

Am I missing something or should I simply buy a 1.5inch skin fitting, drill a hole at the top next to the inspection hatch, fit an elbow and drive the liquids in the tank from the top?
Mind my tank is resting on the keel so there's decent slope and I've secured the pipes in a way that there's no shagging and parts of the pipe that dirty water may rest and eventually mess the pipe.

opinions plz!

cheers

V.

 

[David2452]

If you don't intend to use the DIN fitting for a sender you can get a 1 1/4" BSP adapter http://www.aquafax.co.uk/html/product_specification.asp?ID=23439 to fit it.

 

[Forty_Two]

All mine go in & out at the top which is the only way I would have it.

As you say, bottom equals full pipe plus leak risks. Not acceptable in my world anyway.

Vetus sell what you need to go in at the top if there is room.

 

[vas]

If you don't intend to use the DIN fitting for a sender you can get a 1 1/4" BSP adapter http://www.aquafax.co.uk/html/product_specification.asp?ID=23439 to fit it.

David, i'm planning to go N2K and buy a Maretron TLM100 ( http://www.maretron.com/products/tlm100.php ) sensor, hence my idea of drilling a hole and adding a skinfitting upside down in there

All mine go in & out at the top which is the only way I would have it.

As you say, bottom equals full pipe plus leak risks. Not acceptable in my world anyway.

Vetus sell what you need to go in at the top if there is room.

thanks, that's exactly my thoughts!

Plenty of space at the top, but not particularly happy to pay vetus for something relatively straightforward (skin fitting and elbow will probably set me back 4-5euro...). Thanks for the pointer though, will check their catalogue in case there's something really clever that I must get!

cheers

V.

 

[jfm]

All mine go in & out at the top which is the only way I would have it.

As you say, bottom equals full pipe plus leak risks. Not acceptable in my world anyway.

+1. I'd just get some extra fittings for the top of the tank

 

[vas]

continuing on the same thread for consistency...

so, decided on tank placement (eventually turned in round 180 degrees so that I can have the hatch on the aft which means I can access the hatch with only lifting the bed mattress and floor (and not disassembling the whole bed...), drilled the hole (it's a good 6mm thick material, guess it will last for a good while!) and now have a final Q.
How do I seal the joint?
I can cut a rubber seal/flange (out of a car/bike/pushbike innertube) and fit it inside the tank
I can use Sika 221 sealant on the inside again.
I can do nothing and simply tighten the hard GRP flanges one another (but I'm pretty sure there's going to be some smell...)

so, any reason I shouldn't do the first or second option???

tank and hole :

cheers

V.

 

[rafiki_]

Vas, I would use PTFE tape for sealant. If not this then the Sika sealant, but that is messier, and will need cleaning up if you ever need to access the fittings. I think a bit of bike inner tube will perish quite quickly.

 

[vas]

Vas, I would use PTFE tape for sealant. If not this then the Sika sealant, but that is messier, and will need cleaning up if you ever need to access the fittings. I think a bit of bike inner tube will perish quite quickly.

Paul,

hole is 2mm larger than the threaded part of the inset. Two flat flanges one on each side clamp it together.
How am I meant to use PTFE tape??? It usually goes to the threads, but wont do much on the actual sealing between the blue polywhatever material and the GRP of the elbow unless I wrap a whole tape conically around the bottom flange and threads...
Will probably use the 221 and be done with it. Not too worried getting a bit dirty you know and I doubt I'll ever need to do something with this fitting (unless it leaks!)

cheers

V.

 

[jfm]

Vas
I agree you shouldn't use ptfe tape. That is only for sealing threads, which isn't the issue here

I also wouldn't use rubber gasket made from inner tube. The surface of the rotomoulded tank is likely too rough and when rubber is that thin the gasket is too stiff/will not deform and wouldn't seal wonderfully well - at least not in a controlled way - you'd be relying on luck

I'd definitely use sikaflex 221 or similar here. You have good access and can nicely smooth the inside sealant to create a good bond area. As a minimum I would clean the plastic tank material with acetone or something in case it has silicone mould release agent on it, thus getting a better sikaflex bond. If you want to be very fussy you could use sika's primer but tbh I wouldn't bother because it is €50 a tin and these joints aren't even immersed or pressurised most of the time