Step down hose outlet to increase flow

[afroturf]

I've just watched the most recent youtube video by Aquarium design group, 'small aquarium strategies' and the associated live stream. One thing most notable from the video is they often stepped down the filter outlet size to increase flow, in the livesteam video Jeff Senske mention many well know filter manufactures have potentially oversized the filter hose in the eyes of an aquascaper where good levels of flow is often important. Having had a minor niggle with the flow on my 250l tank and having a spare 12mm filter outlet I swapped one of the 16mm outlets fitted and have to say I'm quite impressed with the difference, I understand that I may have lowered the overall output of the filter but certainly the velocity of the water leaving the outlet has increased.

Thought this may be of interest to some people and perhaps something many people may have overlooked when having issues with flow, link to ADG youtube channel

https://www.youtube.com/channel/UCdUMTaEJi3o67IllKhaKJww

 

[Garuf]

Americans often use filters us British/Europeans would consider undersized, I would imagine that this is a way to counter that, you often see many a 60p or similar with a 2213 for example, perhaps this strategy is just a way to counter this tendency to undersize filters?
I’ve done the reverse in practice and put 17mm outlets ex700’s to reduce the velocity when not using lilies.

 

[DogTailRed2]

When I contacted OASE about decreasing flow on their filters they recommended reducing flow on the inlet only.
This implies restricting the flow on the outlet might be bad?
As reducing the outlet is effectively reducing the flow for the benefit of greater force it might be putting strain on the pump.
I always feel that using the filter as intended is best for longevity.
Interested in other opinions on this.

 

[ceg4048]

I've just watched the most recent youtube video by Aquarium design group, 'small aquarium strategies' and the associated live stream. One thing most notable from the video is they often stepped down the filter outlet size to increase flow, in the livesteam video Jeff Senske mention many well know filter manufactures have potentially oversized the filter hose in the eyes of an aquascaper where good levels of flow is often important. Having had a minor niggle with the flow on my 250l tank and having a spare 12mm filter outlet I swapped one of the 16mm outlets fitted and have to say I'm quite impressed with the difference, I understand that I may have lowered the overall output of the filter but certainly the velocity of the water leaving the outlet has increased.

Thought this may be of interest to some people and perhaps something many people may have overlooked when having issues with flow, link to ADG youtube channel

https://www.youtube.com/channel/UCdUMTaEJi3o67IllKhaKJww

Hello,
The mass flow rate, or, throughput of the pump can be limited by the smallest orifice size in the circuit. Take care when discussing flow to distinguish between velocity and mass flow as they are different. You can restrict the holes in a spraybar, for example and this will produce a faster nozzle speed, but less water is flowing through the system. As a result, this reduces the overall effectiveness as this reduces the actual filtering capacity since less water will be in contact with the filter media and less water will be sent out to the tank for distribution.
Typically, the minimum orifice (restriction) size is at the filter's output nozzle, say, 12mm for example. If a larger diameter tubing is used this will not affect the mass flow rate, but will lower the velocity and dynamic pressure. Stopping the tubing back down to 12mm will increase this pressure and will increase the velocity. again, if, anywhere in the circuit, the diameter is lowered beyond the 12mm then this is essentially choking the filter. Think about your garden hose with a nozzle. When you turn the nozzle towards closing you are shrinking the orifice, so the spray exits the nozzle faster but less water exits the nozzle as well. I'm not aware of filter exit nozzles that can be increased because the hole that the nozzle is screwed into is fixed, typically. If there are variable hole sizes and they can be enlarged then this is a great feature and should always be used to improve mass flow rate.

When I contacted OASE about decreasing flow on their filters they recommended reducing flow on the inlet only.
This implies restricting the flow on the outlet might be bad?
As reducing the outlet is effectively reducing the flow for the benefit of greater force it might be putting strain on the pump.
I always feel that using the filter as intended is best for longevity.
Interested in other opinions on this.

Yes, I agree. Restricting the exit side back-pressures the pump.

Cheers,

 

[afroturf]

Hello,
The mass flow rate, or, throughput of the pump can be limited by the smallest orifice size in the circuit. Take care when discussing flow to distinguish between velocity and mass flow as they are different. You can restrict the holes in a spraybar, for example and this will produce a faster nozzle speed, but less water is flowing through the system. As a result, this reduces the overall effectiveness as this reduces the actual filtering capacity since less water will be in contact with the filter media and less water will be sent out to the tank for distribution.
Typically, the minimum orifice (restriction) size is at the filter's output nozzle, say, 12mm for example. If a larger diameter tubing is used this will not affect the mass flow rate, but will lower the velocity and dynamic pressure. Stopping the tubing back down to 12mm will increase this pressure and will increase the velocity. again, if, anywhere in the circuit, the diameter is lowered beyond the 12mm then this is essentially choking the filter. Think about your garden hose with a nozzle. When you turn the nozzle towards closing you are shrinking the orifice, so the spray exits the nozzle faster but less water exits the nozzle as well. I'm not aware of filter exit nozzles that can be increased because the hole that the nozzle is screwed into is fixed, typically. If there are variable hole sizes and they can be enlarged then this is a great feature and should always be used to improve mass flow rate.

Yes, I agree. Restricting the exit side back-pressures the pump.

Cheers,

I understand what you are saying, I am a laymen when talking about this I was only impressed with the extra velocity achieved when may be stopping down the filter hose size as this was something I wanted to improve with out upgrading the filter or adding a pump in the tank. Stopping down the hose should lower the overall flow through the filter but then again maybe it may not have to much of an impact, I'm not going to do any experiments but I doubt any filters run at the max possible flow rate trough the give hose size so maybe stopping down the hose size would be too detrimental to overall flow through the filter