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25mm or 32mm bulkheads?


wolvo23

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Things to ask yourself:

Were will teh bulkhead sbe located, if at teh top of teh tank tehy will need to be bigger to allow more water to flow out

with centres at 3-4cm below water surface out flow will be about 400/450lph for 25mm bulkhead inner size is about22mm

a 32 mm bulkhead inside size about 27mm allows lots more outflow ~ 700lph each

If they are in the bottom of the tank and utilising a standpipe setup than a 32 mm bulkhead will allow >1500lph flow down it, a 25 maybe 800lph

You then need to work out what you want your turn over rate to be?

How big a pump are you going to have to get to allow this turnover rate?

piping from tank to sump will need to be adequate to cope, I would dump into 110mm raiwater pipe with 32mm bulkheads as standpipes.

a bit noisy but effective.

or have each dump pip drai directly to the sump, so 6 feed lines to sump.

Are you going to use bulkheads as you inlets??? or just have it pour in the top?

So tank size and stocking levels will dictate you turnover rate, and sump requirments, and that will dictate your pump requirments, which will dictate the outlets required to keep up..

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Hey wolvo,

If you have the option, go for the bigger drains and pipes. There is nothing worse than not being able to push enough water through your tanks because your drains aren't big enough to handle the flow.

Cheers, Doug

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Hey wolvo,

If you have the option, go for the bigger drains and pipes. There is nothing worse than not being able to push enough water through your tanks because your drains aren't big enough to handle the flow.

Cheers, Doug

In short, drill holes the next size up and fit with the bulkhead fittings to match this-up sized hole. Then plumb both sides DOWN to match your pumps size inlet/outlet. That way if in the future you decide to put a bigger pump on or a pump with different inlet/outlet sizes, you won't get stuck with a hole too small with no way to make it bigger.

It will cost a little more as a bigger sized bulkhead will cost more but it is insurance for any future changes, and if it is never required can have no downside.

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Agree with all the good advice above. I made the mistake of plumbing a rack of 5 tanks of mixed sizes (approx 800ltrs total) with 25mm pvc up and down to the sump. I had to limit the pump with taps on each outlet at the top tanks as the gravity flow back wasn't sufficient with 25mm outlets. This is using a 4900l / hr pump with a height of 2.3mtrs. Think the 32 and 50mm will be plenty but simply down pipes need to be bigger than the upflow pipes. 25mm up would match well with 32mm outlets into 50mm collection pipes. My other recommendation would be to have pvc ball type taps on each tank at the top. This isn't to limit the total flow but to regulate equal flow between all tanks. Hope this helps not adds confusion?

Cheers Couchy :thumbup:

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