# Would this design work/make sence?



## Linoleum (Aug 9, 2009)

I want to have an inlet at the surface of the tank and one that bottom. Have i got it right? Or would my sump overflow if the pump went out and the tap was on?

I am currently in the planning process of a monster tank. I have gathered most my info from TFG's tank, thanks man :wink:


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## Mcdaphnia (Dec 16, 2003)

When the water level dropped to the top intake, it would begin admitting air which would break the siphon and stop water flow. Unless some chunk of something was completely sealing off the top intake.

It's safer to have just the top intake and put a box with slots at top and bottom around it. Or use a vertical pipe inside the tank with openings near the top and bottom that connects to the intake with a tee fitting.

Don't put any holes in glass close to the edges. It's better to have a sump capable of holding the top several inches of water from the tank.


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## Linoleum (Aug 9, 2009)

its going to be plywood so i figured i could put holes anywhere? why just a pipe inside?


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## mightyevil (Oct 23, 2008)

If I am interpreting what you are trying to achieve correctly then...

You would need more than one or two holes IMO because the suction power that one whole or two will create could possibly suck fish or other living things and eventually maybe even clog it. I would consider making an overflow box, it would work better and IMO probably cheaper that buying multiple bulkheads instead of just one big bulkhead.

If you are convinced that you want the design you have on top, I would just change the bottom pipe to be horizontal to the top pipe.


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## Linoleum (Aug 9, 2009)

The point of having the an inlet at the bottom is to suck water from the bottom for the tank which would contain waste matter which the top inlet would not get. I was planning on having these inlets at each end of the tank, the fish going in there would not get sucked in.


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## Mcdaphnia (Dec 16, 2003)

Linoleum said:


> The point of having the an inlet at the bottom is to suck water from the bottom for the tank which would contain waste matter which the top inlet would not get. I was planning on having these inlets at each end of the tank, the fish going in there would not get sucked in.


The top bulkhead can certainly suck up detritus from the bottom of the tank. If there is a box around it with slots at the top and bottom, it will draw from both areas. The box advantage is that it's unlikely anything would simultaneously block all the slots. A standpipe open at top and bottom would also work.


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## Linoleum (Aug 9, 2009)

ohhh ok, i understand your idea now. with this box or stand pipe i would still have to have the pipe to the sump going up to water level wouldnt I? to prevent the sump over flowing.


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## Mcdaphnia (Dec 16, 2003)

It's not just the pipe going up to water level that determines the siphon break. It's the highest point that air can enter the pipe. so there has to be a small hole or an upwards facing tee to admit air into the pipe at the level you want the siphon to break. Without that opening, you could run the pipe to the ceiling and the water would still drain out until it reached the highest bulkhead fitting.

In plywood tanks it's best to have the holes for bulkhead fittings close to the top of the tank where water pressure is lower. The further down the fitting is placed, the more likely it is that seepage will damage the plywood. This seepage would not be noticeable and in a glass or acrylic tank could do no harm. If I was going to have any bulkhead fittings in a plywood tank, I'd have them high and be sure to use MDO plywood for the tank. Medium Density Overlay plywood, not to be confused with MDF which is just fiberboard, uses a better adhesive inside than exterior plywood and has a smooth coating on the surface so it helps get a better seal on the gasket of the bulkhead fitting.


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## mel_cp6 (Feb 3, 2009)

i really cant see this working.
water level in inlet 2 will always be at the same level inside the display tank.
inlet 2 will only start to drain when water reaches the top, but by putting a T connected to 
inlet 1, your only really draining from inlet1. making the inlet 2 useless.

what i would do to be able to drain the bottom is NOT connect them together, but 
put a T (connected on one of its inlet, install it sideways) connected to the inlet2.
but you have to be absolutely sure that inlet 1 is at the same height with inlet 2 when they
are draining. otherwise, only 1 drain will work.
if inlet 1 is a bit higher, inlet 2 will not work and vise versa.
ask the fishguy for his design.


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## mel_cp6 (Feb 3, 2009)

here i found it.









so this would be your inlet 2. this design also has a drain valve. very usefull if you ask me.
you can put the hole closer to the bottom of course.
so you can install inlet 1 on its own but it has to be align to the horizontal pipe (maybe a bit higher)
i would try it on a tote box 1st to see if both drains will work properly before i start 
putting holes on your tank.

hope that make sense. i like your idea but your design will not work but with minor adjustment i think its a great idea.

i was also thinking of the same thing before. i wanted a tank that can drain from the bottom and at the same time be able to skim the top. now i think 
with adjustments on your design and incorporating it with "fishguy's" design i think it may just work.


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## Linoleum (Aug 9, 2009)

Ok im beginning to understand what i have to do, thanks to all your help and patience  
So let me get it straight:
Each inlet will need its own pipe to the sump. 
Inlet 2 will need to have a T with an air hole at the top to break the siphon.
Both the pipes need to be the same hight for both inlets to drain simultaneously.

Does inlet 1 also need a air hole or will it be fine because the water level will just drop below it?

I am concerned about what Mcdaphnia said about having bulkheads in ply wood, i was under the impression that they are fine? Seepage would be water getting between the layers of plywood right? Is there any way to get around this without losing the lower inlet?

Thanks for taking the time to find that diagram mel :thumb:


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## Mcdaphnia (Dec 16, 2003)

Actually I don't agree with the idea that two drainholes plumbed together will only let one work. Both will drain, but the lower one, separate or linked, will drain more water because of higher pressure. You could have interference only if you used very small diameter pipe.

There used to be a lot of plywood tanks in the hands of hobbyists around here. Not so much anymore. Those with bulkheads commonly had problems. While it doesn't matter on a glass or acrylic tank, the gasket has to be on the inside of a plywood tank. Some actually didn't think of this until there was deterioration.


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## mel_cp6 (Feb 3, 2009)

> will drain more water because of higher pressure.


pressure inside a tank is all the same regardless of the height. 
i think its under "Pascal Law" or something like that.
i remember this back in college. but hey i could be wrong.

some one should ask thefishguy for advice.

the inlet2 is just acting as a extention of the tank, so it will only drain once
its at the same level as the drain pipe. but with the inlet1 connected to this, it can not drain
because it will be draining from inlet1.

but you know what, its up to linoleum what he wants to do. 
like i said give a try on a tote and see if it would work. the problem with them being linked is
you wouldnt know if inlet2 is draining at all.


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## Mcdaphnia (Dec 16, 2003)

Sorry Mel. Good memory, but not the applicable law. You are right that the pressure of water or any incompressible fluid is the same anywhere on the walls of a completely enclosed container. That's what makes hydraulics work to stop our cars and lift the buckets of 'dozers. An aquarium is not a completely enclosed container so Pascal's Law does not apply. Instead pressure increases with depth in bodies of water like the ocean and an aquarium.

It would be easy to test if the holes are draining. Stir in some detritus from an established tank and you will see it being sucked in. Unless you overdo it. :wink:


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## mel_cp6 (Feb 3, 2009)

yes thats correct, i got it from hydraulic class.
i still cant see it working if it was linked like the original design.

it would be good if this will actually work because draining the bottom water 
plus skimming the surface water will be beneficial.
you can drain dirty water plus floating debris at the same time.


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## Linoleum (Aug 9, 2009)

With bulkheads i assumed they would still need adequate sealing inside and outside the joins otherwise obviously water would get into the ply and gaskets are meant to prevent this, also i would water prof the entire hole before i put the bulkhead in.

Anyone else have any comments on how water pressure effects bulkheads?

I thought everyone was making ply tanks these day, i thought they were stupid but then i haddent thought of attempting a 1500gal project as i am now. I don't ant to drag this out too long but i have alot of douts in my mind.


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## Mcdaphnia (Dec 16, 2003)

From about 120 to 500 gallons, plywood tanks are usually the most "gallon per buck". Concrete tanks are probably the best for tanks larger than 500 gallons, certainly when you get above 1000 gallons. Of course tanks just aren't cheap.

Clubs around here used to hold plywood tank workshops, and you'd see many people building their first plywood tank at one then building more on their own.


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## Linoleum (Aug 9, 2009)

wel theres no way im building a concrete tank hahaha


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## Mcdaphnia (Dec 16, 2003)

This is one way to build a concrete fish tank.

http://www.hagblomfoto.com/article_concrete.htm


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## Linoleum (Aug 9, 2009)

not to keen on laying bricks in my house hahaha. Ill stick with ply for this project :thumb:


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