Bulkheads

[@ombomb]

I have been trying to find somewhere that sells bulkheads in the UK but cannot find anywhere that sells the size I have in mind. I am planning on running a 16mm tube from my main tank to the sump and a 12mm return and cannot find bulk heads in that size.

Please can someone point me in the right direction as the smallest I can find are 20mm.

Thanks

 

[andywg]

Fish Fur and Feathers is one of the best online shops for hard plumbing. Think the site is http/www.fishfurfeather.com/

Not too sure if you will have any much luck with 12mm return...though you can always use Eheim flexible for that size...

HIH

Andy

 

[onemisterchristian]

Maybe you already tried this, but i got my bulkhead off of ebay.

 

[@ombomb]

Thanks for the replies on this, I will have to go with 20mm bulkheads, one of which I reduce down to 16mm for the return.

 

[Matthew5664]

If the return is 16 up to 22, what is the size for the flow to your sump?

I'm in the constrution stage of my new set-up and was wondering what your going to use?

 

[@ombomb]

I was planning on keep the flow to the sump at 20mm and seeing how it goes, having said that, I may also reduce it down to 16mm if the flow seems too high as the pump I have for the return is adjustable.

 

[Matthew5664]

I'm using 20mm return from the sump and a 40mm flow with ajustable ball valves to regulate flow.

Read somewhere that 2:1 ratio is good guide line for the flow and return of a sump

 

[@ombomb]

I understood that should be aiming for 2:1 in terms are flow, not 2:1 in terms of diameter.

 

[Matthew5664]

With a ratio of 2:1 of flow rate you my find the return pipe work at 22mm has a max flow rate of 1500lph
So if the flow to the sump is the same diameter then you have the same rate of flow (same goes in as comes out)

By using the ratio 2:1 with the pipe diameter you straight away have doubled the flow rate to the sump compared to the flow rate from it.

Therefore diameter of pipe in directly proportional to the rate of flow ( twice as much can go to sump as can come back)

And therefore less adjustment needed with ball valves.

 

[@ombomb]

Surely thought the flow is proportion to the area of the pipe, not the diameter.

 

[Matthew5664]

By area do you mean cross section area?

Because the area is derived from the diameter! (Area is equal to Pi R squared)

Anyway At Collage we always graded the flow rate by the diameter of the pipe.

 

[@ombomb]

Yes, so as an example:

10mm diameter:

3.142 * 10² = 314.2 square mm

20 mm diameter:

3.1142 * 20² = 1256.8 square mm

so doubling the diameter quadrules the area of the cross-section which means 4 x the flow.

For my original plan:

12 mm diameter:

3.142 * 12² = 452.45

16 mm diameter:

3.142 * 16² = 804.15

Which is closer to the 2:1 ratio.

 

[andywg]

There is no way you need two to one on the diameter, or else marine tanks would just get silly.

Eheim pumps come with a 16mm (internal) fitting for the outlet and a 22mm for the inlet. Not a 32mm inlet.