Eheim + Lilly pipe Velocity problem

[amkr]

Hi,

I previously had an Aquis 500 on my 2ft tank, recently I got myself an enormous Eheim Pro 3E 350 (16mm hoses).

but I had 13mm lilly pipes. So I stepped these down to 13mm using an adaptor to get them to fit on.

The problem I have though, is that even on the lowest pump setting, I've got a bit of a strong water current.

so I've been trying to work out how to best remedy my water velocity problems.

This is the outflow I have currently (13mm)

Im wondering if a straight swap to the 17mm lilly pipes will reduce the velocity? I've also noticed that CAL have an outflow with a larger bell mouth, I'm not sure if that would reduce the velocity aswell.

Anyone have any ideas or suggestions?

[Squiggle]

Yeah a larger pipe will definitely reduce the velocity, reducing the size of the hose going to the one you're using now is causing the problem, just like putting your finger over the end of a garden hose causes higher pressure & more spray, same thing is happening in your tank :victorious:

[BlueBolts]

Thoertically, there's a few solution, depending on the decrease in flow %...

1. An inline tap to restrict the flow. Depending on the severity, this may cause stress on the pump, but conservatively, if you're decreasing it only by 5-10%, it shouldn't cause any issues.

2. If you use say a 13mm pipe, this will cause more water friction running through the pipe (in comparison to a 16mm), thus decreasing the water volume, but not neccesarily the velocity. So using a 13mm pipe onto a large mouth lilly pipe may solve the issue....again it's dependable upon how much you're trying to reduce it by..

3. lengthening the hose, thus causing more water friction....

4. Ditch the lily pipe, and go for a spray bar.

Hope this helps.

[amkr]

Its one of those fangled eheim electronics, so impeding it with a tap isn't ideal, the filter has a feature where it increases speed to counter reduced flow from filter media.

I *think* the reduction in hose size is causing the increased velocity.. it sort of makes sense to me. I just want to be certain before I fork out for larger pipes.

I could lengthen the pipes I guess, they would stick out the side of the tank abit though.

No spraybars, Lilly pipes look nicer :)

[KiwiBigD]

The larger outlet is the better choice, you'll have a reasonable flow but not excessive as compared with the 13mm ones. Do bear in mind the

circumference on a 13mm outlet is 40.84mm whereas 16mm is 50.24 an increase of 20 - 25% roughly as you're trying to squeeze more

flow through the same tubing so the speed will increase. These numbers aren't strictly accurate as I'm not sure whether that is the inside or

outside diameter but either way increased speed and pressure due to flow restriction. It will add in a decreased life of your filter. Whereas

going to 17mm the pressure will stay the same as the 16mm as the pump won't be restricted.

[amkr]

At the moment I've got a bit of 16mm eheim hose stuck infront of the outflow to break up the speed a bit which seems to work.

I'm hoping a 17mm outlet will cut the speed down to somewhere around the same velocity. I just don't want to spend the cash to find out it doesn't work.

Otherwise the only option I can think of is that wierd ass circular thing from ADA =/

[blindfisherman]

The larger outlet is the better choice' date=' you'll have a reasonable flow but not excessive as compared with the 13mm ones. Do bear in mind the

circumference on a 13mm outlet is 40.84mm whereas 16mm is 50.24 an increase of 20 - 25% roughly as you're trying to squeeze more

flow through the same tubing so the speed will increase. These numbers aren't strictly accurate as I'm not sure whether that is the inside or

outside diameter but either way increased speed and pressure due to flow restriction. It will add in a decreased life of your filter. Whereas

going to 17mm the pressure will stay the same as the 16mm as the pump won't be restricted.[/quote']

wouldnt it be better off going off the cross sectional area of the pipe. 132 mm^2 for 13 and 200mm^2 for 16mm...

So there is quite a significant difference in the area and therefore velocity.

the good old equation Q=(rho)*A*v.

so as the area decreases, for the same mass flow rate (q) the velocity is inversely proportional.

I would say that increasing your pipe to 16mm would approximately bring the velocity of the flow down by 1/3

[amkr]

wouldnt it be better off going off the cross sectional area of the pipe. 132 mm^2 for 13 and 200mm^2 for 16mm...

So there is quite a significant difference in the area and therefore velocity.

the good old equation Q=(rho)*A*v.

so as the area decreases' date=' for the same mass flow rate (q) the velocity is inversely proportional.

I would say that increasing your pipe to 16mm would approximately bring the velocity of the flow down by 1/3[/quote']

This is why I wish I did physics =/

1/3 sounds like good numbers, i'm just hoping its enough.

[mr_c265]

You could use a larger lily pipe, or a 3 way T and run two lily pipes.

All of the above ideas are correct by the way, they will all work. As will lengthening the hose to increase friction, using a narrower hose and adapters to add frictional pressure from expansion and contraction fitting losses as well as the friction from the increased water flow velocity.

I know you love maths Mark, so Q=U*A, Re=rho*U*d/mu for fully developed laminar flow, f=16/re and deltaPfriction=(4*f*l/d)*rho*U^2/2 and then use delta p friction = rho* delta U^2/2 to work out how much the water will slow down based on the added friction.

But the best way you can reduce the flow is to face the outlet towards the backglass, it'll disperse off there and circulate evenly around the tank still.

[blindfisherman]

This is why I wish I did physics =/

1/3 sounds like good numbers' date=' i'm just hoping its enough.[/quote']

the only issue is... i have been at the pub for a few hours so my maths may be a bit dodgy

[amkr]

Yeah those laminar flow calcs aren't happening. I'm just going to stare at the formula wistfully and pretend im doing it in my head...

I really like that T adaptor idea! I didnt think of that at all.

I'll grab a set of 17mm pipes tomorrow and some extra hose (and a T piece if they have one). I think I'll position the pipes at the BACK of the tank facing forwards, it has less distance to travel before it hits a wall then. Will need to have a play and see what works best.

Whats the best configuration to run the 2 pipes in? 2 on one side and the inlet on the other?

[amkr]

Settle down you lot.

I'm going to have to get a mod in here soon to delete all the maths posts so I don't look like so much of an idiot :dejection:

[torface]

How did you go with this, Mark?

[amkr]

Grabbed the 17mm pipe tonight, haven't fitted it yet though.

been busy watching Django!

[torface]

Grabbed the 17mm pipe tonight' date=' haven't fitted it yet though.

been busy watching Django![/quote']

Such a good movie!

[amkr]

hell yeah, I lost it when he got to pick his own clothes... comes out in the bluest pimp suit possible.

Then at the plantation the girls like "It's bad he makes you wear that" - "I'm free remember" - "wait... you choose to dress like that!"

[torface]

LOL yeah!

Some of it's pretty shocking. I got really pissed off at what happens with the German dude at the end though...

[amkr]

thats Tarantino for you, can't have a happy ending :p

[mr_c265]

Good movie! All the Tarantino films are top quality.

[2OFUS]

LOL yeah!

Some of it's pretty shocking. I got really pissed off at what happens with the German dude at the end though...

Im guessing you are German Torface ???

[torface]

I'm half German, but that's not why I was pissed off... I dont want to spoil it for anyone who might not have seen the film, but I was disappointed with his behaviour lol

[MrShrimp]

With all this talk about dtango, I want to see this movie now.

[torface]

It's a good movie. Kinda shocking, but good lol :)

[amkr]

I was sort of hoping the German had some scheme up his sleeve. His death seemed a little out of character.

I added the 17mm pipe, its bloody huge but its cut the velocity down alot. I'd like to cut another 15% off it still though.

Im thinking of re-arranging the under cabinet goodies to cut it down a bit more.

Currently I have

FILTER --->(17mm)HEATER(17mm)--->(17mm)(13mm)REACTOR(13mm)(17mm)---->(17mm)Lilly Pipe

Im thinking maybe the 13mm reactor being the last exit may be increasing it a tad, so thinking changing to

FILTER --->(17mm)(13mm)REACTOR(13mm)(17mm)---->(17mm)HEATER(17mm)--->(17mm)Lilly Pipe

Which gives it a longer period of time in a larger diameter hose.

But my physics sucks something savage so this may not make a difference... whats everyone think?

[mr_c265]

Smaller diameter hoses increases the friction, increases the velocity and add's what is known as fitting losses to the water through rapid contraction and expansion. If i was you i'd keep as much 13mm hose as possible.