water flow

[Jeremy]

First want to say HI all been it has been awhile. :D


Is there a formula for how much water flows through a certain size pipe. I have a overflow idea for a river tank. Need to know how many or what size pipe for the pump. Size of pump yet to be decided due to tank size still in question.

[Diana]

I know that such information can be figured out, it is done for irrigation, for example.

I run 1000 gph pump through 1" pipe for my pond, about 4' head.
I run a smaller pump 300 gph) through 1" pipe, but a lot more fittings, more obstructions, on my 72 gallon tank.
Most of the tubing for my larger canisters (rated in the upper 200gph) have tubing that is about 3/4"
Smaller filters (100-200 gph) have intakes of about 1/2".

I know that this is not the same as a formula for pressure loss in various pipes and fittings, but it might get you started.

How many gph are you looking at, and what sort of configuration?

Smaller pipe has more pressure loss than larger pipe, so if you ran say 100 gph through 1/2" pipe and through 3/4" pipe your system would be more efficient with the 3/4" pipe.

Fittings that change the direction of the flow, and change the smooth inside of the pipe cause pressure loss. A long, sweeping elbow is better than a sharp bend. The fewest fittings you can get by with are better.

[shari2]

Hi Jeremy!

Can't help with the math, but just wanted to say nice to see you back.

[Jeremy]

Thank you Diana haven't decided on size of pump or even tank size yet. But what I am wishing to do is similar to a saltwater gravity overflow filter system with modifications. To do a high amount of water flow I have to find how much water I need to drop from the main tank into the filter tank to make sure the pump dose not run dry, or on the other side has enough gph so it dose not over flow.

Thank you for the welcome Shari2.

[Graeme McKellar]

Hi Jeremy, I am no expert in such things but have been researching to set up a similar system myself. The main problem seems to be getting enough flow from the tank to the sump so the more outlets (bulkheads) and the larger size (25mm+) will help to acheive better flows. When setting up the pump return line a tee-peice is placed in this line with a valve and piping returnig to the sump. Your return pump can be rated higher flow than this but can be regulated by opening this valve and returning some of the flow back into the sump. You will have to keep an eye on the water level in the sump as this is were the level drops with evaporation. Ceers Graeme.

[jones57742]

Fellers:

There are two very good web pages out there
http://www.geocities.com/Eureka/Concour ... azen2.html
which is for pipes.

I have run into several head loss calculators for head loss through fittings but they were very cumbersome to use.

What is much easier to use for me is the concept of equivalent length.

An example is a standard 90D bend is equivalent to 5.2 feet of pipe for a 1" pipe.

For our glued PVC fittings the first table at
http://www.engineeringtoolbox.com/resis ... d_192.html
is appropriate.

Fellers:

I did not post earlier because the free fall through a pipe is a completely different creature and from

I have a overflow idea for a river tank.

I did not want to get Jeremy screwed up.


If yall are asking about pressure flow then the previously cited web pages will be appropriate.

Each pump has an associated head/discharge curve and an example is set forth at
http://www.iwakiwalchem.com/nav/CMImage ... 30Rcrv.pdf
which is the curve for my external pump.

Utilizing the head loss through pipes and the pump curves the determination of the correct pump can be accomplished.

The above may sound complicated but when you have done it once it is actually as simple as arithmetic and I can walk you through it the first time.


One last item fellers.

Yall seemed to be focused on losses through piping (dynamic head loss) but static head losses should be added to the dynamic head loss to yield the Total Dynamic Head (TDH is the acronym indicated on the pump curve).

TR

[Jeremy]

Jones the tank would be a free fall, and like you said a different creature. Thank you for the links. It has been years since I had to do any kind pump of these aplications, and even then it was more installing for me it was already figured out before it got to me.
Is there a way of calculation for how much will flow in a free fall at skim height? Higher water level equals more flow because of a higher cascade effect.
Or is this going to end up a trial and error endenvor?

[Diana]

I have 2 tanks that do this.
One is a 72 gallon that is drilled.
It has an 1-1/4" overflow kit. The water falling through this is not fast enough, I have a 300 gph pump, and need to keep it turned down. Not by much, though. I suspect the inlet is not big enough. Not enough area for the water to enter the pipe.

The other is a 125 with a DIY auto-restart over the edge siphon, using 1" PVC pipe. The inlet is different and a lot longer than the kit for the other tank, and a 300 gph pump worked just fine for that. The inlet that I made for this tank is about a foot long, and is almost all holes. Just enough mass to keep the fish out. It sits at the top of the water level, so as the pump fills the tank the overflow starts.

On both set ups there is a kill switch that turns off the pump if the sump runs low. Evaporation can lower the volume enough to turn the pump off, and one sump was just the right height for my dogs to drink out of.

[jones57742]

Jones the tank would be a free fall, and like you said a different creature. Thank you for the links.

Jeremy:
Thanks for the comment as it took more than a minute or two to get the post together.

Or is this going to end up a trial and error endenvor?

Jeremy:

It is not 100% trial and error.
When I have a better idea of what you are up to I believe that I can help.
(ie. I do not know not which of (or multiple of) the various equations should be employed).

As I do not know the particulars of your thinking I cannot say this for certain but I believe that the main problem which we will face here is the noise from the overflow configuration (sounds crazy doesn't it).

TR

[Tinman]

The main problem seems to be getting enough flow from the tank to the sump so the more outlets (bulkheads) and the larger size (25mm+) will help to acheive better flows

I have a pick up on the suction side of the pump inside each tank increasing flow rates by multiples and overcoming the problem of low flow out of a tank. I use the bulkhead overflows to balance the flow in only allowing flow in to equal my suction tube plus any amount my bulkheads will flow. The flow rate through a pipe is limited by pressure applied so the lower in a tank with the bulkhead the more you will flow in a gravity feed situation .More than a surface skim type bulkhead and overflow .

In my case on some tanks I have siphon boxes over the sides to avoid the issues of small bulkheads altogether and drilling with multiple 2" siphon tubes to attain flows that never matched or came close to when I started removing water from a tank via pump also.

[crazy loaches]

Gravity drains are a little different. Reef sites will have tons more info since thats pretty much the norm there. You can search for overflow calculators like:

http://www.aquariumpros.ca/modules.php? ... Calculator (just a calculator)

http://www.reefkeeping.com/issues/2003-07/gt/index.php (lots of great info there and theory)

http://www.reefcentral.com/calc/ (various calculators for marine stuff, including some drain size calcs etc).

[Dave C]

I've run overflows to sumps in both f/w & s/w tanks. I ran them in f/w using overflow boxes & drilled tanks. In general a 1" pipe in an overflow box will drain 600gph. (larger pipes will carry substantially more flow, a 1.5" pipe is about double that, a 2" about 4x). Since the box has a large area for the tank to overflow into the pipe is usually solid water and will reach the 600gph flow rate. But drilled tanks suffer from air in the overflow pipe and will get much lower flows. My s/w tanks had overflow boxes glued to the tank with the bottom of the box drilled. These worked the best as they had huge area for overflows and the drilled box managed to get maximum flow through the pipe.

The size of the hole/pipe will depend on the flow you want to achieve. And the flow will depend on the size of the tank you're servicing. I ran two drilled holes on a 180g tank that had 1" hoses on them running down to the sump. I ran a pump that would do 750gph at the height of 6' and the overflow barely kept up. It's always better to oversize the drain lines to ensure you don't ever overflow the tank. But if you use a reef-style overflow drilled box in your tank and oversize the pipe/hose going to the sump you will not have much to worry about unless you get a stupidly large pump. If your pump has too much capacity you can just Tee off of the return line and run the excess flow back through your biological media to reduce the flow through the tank and increase the biological filtration.

I would also oversize the sump to ensure the risk of running dry is minimal. The larger the sump the more water you will have in there and the more days of evaporation it will take to run dry. The other side of the coin is overflowing the sump. In a power outage situation you can expect about 1" of water to return from the tank. So take your LxW dimensions of your tank divided by 231 to see how many gallons will be coming back when the power is out. Make sure you have the excess capacity over & above the normal water level in your sump to accommodate that water. Bigger sumps are much more risk-free. The one thing I never did with f/w and kicked myself for after getting in reef tanks was auto-refill for my sump. It's brutally easy to have a 5g jug/container of suitable water with a small pump & float switch that can keep the water level in your sump (and therefore in your sump & tank) above the point of running your pump dry. And an extra 5g can mean a lot. In a reef tank you can do it by running water straight from an RO unit so your tank will never run dry but for f/w you can still do it with a container & pump/float switch. It's really cheap & easy to do too. Reefcentral has tons of details on setting that up.

Hope that helps.

[Jeremy]

Thanks all I will be sure to post the pics as it gets built.