Tuning the Ehiem 1250?....

MadDogMe · 09-30-2002, 04:33 AM

Has anyone tried tuning the inlet holes on the 1250?, they are very badly designed I think!, if getting more/faster water to the impellor is important, then definatly badly designed!!.

I'm on about the 'peice' that the inlet barb screws into. it looks kinda like a ...., well I don't know what it looks like so lets call it the 'inlet housing'. it's the round peice with an 'O Ring' on it that clamps and seals onto the pump body with a 'ring~like' retension thingy with four stops on it

.

The inlet housing has qite a large bore but the part that lets water enter into the impellor is made of four small 'slots' around a 'cup' that holds the nylon centre spindle(of the impellor) in place. the bore of the housing actaly narrows down as it nears the 'slots'.
These slots could be 'ported' or 'opened up' quite easily with a dremel or needle files. Has anyone ever done this?. I imagine you could easily double the area that water enters through without weakening the housing at all.

I thought of using a peice of Cu(with hole for spindle, and doing away with the 'rubber gromet' thing) to 'bridge' across the gap instead of the 'too large' cup and rubber design. it would be alot more streamlined and less flow restrictive.

The thing is I want to know whether this is important for flow, whether this is actualy restricting the water flow to the impellor. whether the impellor could shift more water, or wether this has been balanced in the design.(this I doubt considering the nature of the pumps intended usage. it would be easier to just make it bigger , more powerful than to tune it)...

Cathar · 09-30-2002, 04:41 AM

If you think the 1250 is scary, take a look at a 1048 some time.

The shape is kinda like a radiation hazard symbol is how I would describe it.

I've often pondered just the same thing, about widening the holes.

Cathar · 09-30-2002, 04:47 AM

Just pulled my 1250 apart and took a closer look.

The radius of the greater inlet size is 16mm.

The radius of the spindle holder is 11mm.

The 3 structs that hold the middle in place are 2.5mm x 2mm.

This gives a total intake area of:

201 - 95 - 15 = 91mm^2

The ID of the stock 1/2" outlet barb is 10.5mm, or 86.6mm^2.

So basically the inlet holes are less restrictive to the pump than the outlet 1/2" barb.

MadDogMe · 09-30-2002, 04:48 AM

Quote:

If you think the 1250 is scary, take a look at a 1048 some timeThe shape is kinda like a radiation hazard symbol is how I would describe it.
I've often pondered just the same thing, about widening the holes.
.

It does seem to be the biggest stumbling point/restriction on the pump doesn't it?. perhaps someone'll start making an anodized ALu aftermarket tuned jobbie?

...

Quote:

So basically the inlet holes are less restrictive to the pump than the outlet 1/2" barb.

*Edit!!* Are you sure?, it looks to be so tiny when you look at the area of the three(did I say 4 earlier?) slots. the standard outlet is 3/8's is'nt it?...
I read somewhere that there's a 'ratio' for inlet~outlet, and the inlet is supposed to be X amount larger than the outlet. do you think it's tuned?, or just (good old manufacturers~) 'near enough'?...:shrug:

Cathar · 09-30-2002, 04:57 AM

Quote:

Originally posted by MadDogMe
*Edit!!* Are you sure?, it looks to be so tiny when you look at the area of the three(did I say 4 earlier?) slots. the standard outlet is 3/8's is'nt it?...

Pretty sure. Looks can be a little deceiving until you take measurements. This now explains why Eheim use a 5/8" Inlet so as to not restrict the inlet holes which a 1/2" barb simply couldn't match.

The Eheim 1250 uses a 1/2" outlet, 5/8" inlet. I'm positive on that.

MadDogMe · 09-30-2002, 05:01 AM

Another question!, is the outlet the same (standard?) thread as a 1/2inch barb?(1/4BSP~thread?), or is it metric?...

Cathar · 09-30-2002, 05:04 AM

The outlet barb uses 3/8" BSP thread. The inlet 1/2" BSP.

I replaced my inlet and outlet barbs with brass barbs.

MadDogMe · 09-30-2002, 05:06 AM

My 1250 has a 3/8 outlet!,I thought it was 1/2 at first cause my 1/2pipe fitted onto it perfectly, but it's definatly 3/8. If the inlet IS balanced at manufactur, it's balanced for a 3/8 outlet!

. we'll have to port it and see what happens. I can't imagine it would do any harm, and you could always epoxy an 'original sized' thin plate back over the hole

...

************************************************** *********
PS. I don't understand how they come up with thread measurements, can you explain them?. is it to do with the amount of threads in a given 1/2inch.
I read that the Maze3:1 I have has 1/4inck BSP thread, I'd like to understand exactly what it means :shrug: ...

Ignorance is'nt always Bliss!

...

Cathar · 09-30-2002, 05:18 AM

I don't pretend to understand why, but the maximum barb size for a particular BSP thread is 1/4" larger than the thread size given.

For example, a 1/4" BSP thread will allow for a 1/2" barb size with no flow restriction. A 3/8" thread will allow for a 5/8" barb size, and so on.

Go figure.

I didn't invent the standard.

In other words, the Eheim 1250 has a 3/8" BSP thread with a 1/2" barb on it. However, if one so wishes, they can stick a 3/8" thread - 5/8" barb on it.

MadDogMe · 09-30-2002, 05:28 AM

Excelent!, OCPC sell the larger 5/8 (14mm~internal?) barb, I'll have to replace the 3/8 outlet with one. and maybe a 3/4 for the inlet?. definatly have to port the holes then

...

decodeddiesel · 09-30-2002, 04:56 PM

hmm...never really thought about porting and polishing my pump before, but this sounds interesting

Cathar · 09-30-2002, 06:00 PM

Quote:

Originally posted by MadDogMe
Excelent!, OCPC sell the larger 5/8 (14mm~internal?) barb, I'll have to replace the 3/8 outlet with one. and maybe a 3/4 for the inlet?. definatly have to port the holes then ...

Let me clear this up since you still seem to be a little confused.

The Eheim 1250 has a 1/2" outlet barb on it, but the thread on that barb is 3/8" BSP. 3/8" BSP threads are large enough to support a 5/8" barb if required.

Wisked Klown · 10-01-2002, 12:57 AM

Quote:

Originally posted by Cathar
The Eheim 1250 uses a 1/2" outlet, 5/8" inlet. I'm positive on that.

The barbs on it are 3/8" inlet and 1/2" outlet. Here look at this Eheim 1250

110/120V - 317 GPH

1 Fitting is 3/8" (silicon hose)

1 Fitting is 1/2" (silicon hose)

Got that from DangerDen. Plus that I'm running with a 1250 Eheim and I went for the 1/2" inlet upgrade so that they would both be the same.

Cathar · 10-01-2002, 01:14 AM

I was looking at the Eheim 1250 manual that was sitting on my box.

Who do I trust more? The Eheim manual, or Danger Den possibly mis-typing something.

The Eheim 1250 inlet is a 5/8" barb. You just have to look at the pump and you know that the inlet is larger than the outlet.

If DangerDen are saying 3/8" inlet and 1/2" outlet, then they have a type on their page and should correct it.

redleader · 10-01-2002, 02:34 AM

Quote:

Another question!, is the outlet the same (standard?) thread as a 1/2inch barb?(1/4BSP~thread?), or is it metric?...

Standard PVC 1/2 will fit on the smaller fitting. I have never found a supplier in Arizona (and I checked a few) that had anything for the larger one.

MadDogMe · 10-01-2002, 04:20 AM

Quote:

Let me clear this up since you still seem to be a little confused.

The Eheim 1250 has a 1/2" outlet barb on it, but the thread on that barb is 3/8" BSP. 3/8" BSP threads are large enough to support a 5/8" barb if required.

Dude!,I'm not confused!, you were very enlightening

.

The barb (outlet) on my Ehiem 1250 is 3/8~10mm inner diametre, as well as being 3/8~BSP. I have it laying in my hand with a steel rule across it

, I'm not saying they ALL are. if you have the original, dig it out and check what yours was...

I always thought they were 1/2(12mm inner) but I saw on a Web site that they were 3/8(10mm inner) and checked, low and behold!! 3/8!!...

I was thinking of getting a 1/2inch barb to go on there, but I'll settle for a 5/8

.
*******************************************

Quote:

The barbs on it are 3/8" inlet and 1/2" outlet. Here look at this Eheim 1250

Sounds like they're quoting the thread size!.

MadDogMe · 10-01-2002, 04:44 AM

Cathar!, sorry, you're right. I always took a 1/2inch barb to mean 12mm inner, they're not!. the outside diametre of my maze3;1 '1/2inch' barbs is'nt even 1/2inch!!.

So a 1/2 barb is 12mm outer diametre, with a 10mm inner.

It gets confusing seeing 3/8tube advertised as 10mm inner. so infact 1/2inch barbs would be better fitted with 3/8Tube!!, at least the flow would be constant: 10mm > 10mm, Looney!!

...
************************************************** *******************

Seeing this I can understand why the block is 'so' restrictive, it really needs a 12mm inner diametre barb to utilize the full flow

.
The first block I make will definatly use 3/8 thread!!. why are'nt the manufacturers doing this! :shrug: , Crazy!...

Cathar · 10-01-2002, 05:25 AM

Quote:

Originally posted by MadDogMe

Seeing this I can understand why the block is 'so' restrictive, it really needs a 12mm inner diametre barb to utilize the full flow .
The first block I make will definatly use 3/8 thread!!. why are'nt the manufacturers doing this! :shrug: , Crazy!...

The outer channel of the Maze 3 is 9mm wide x 9mm deep, or 81mm^2 cross-sectional area.

With a 1/2" barb (outer-diameter

), that has a 10mm ID, this supplies 78.5mm^2 of entrance area, which almost perfectly matches what the Maze 3 offers internally.

Just to really mess with your head though, I've been playing around with some water-block designs, and it can actually be more beneficial to cut the entrance down to 20mm^2, and live with the large drop in flow rates, so long as you use that flow more effectively (ala mini-jets).

bigben2k · 10-01-2002, 08:59 AM

I just picked up a Little Giant 2-MDQ-SC, and it has 1/2 fittings, in and out. I picked up CPVC fittings at Lowes, and a good 1/2 barb with 11.5mm ID at Home Depot. Lowes sells cheap 1/2 barbs that are seriously undersized.

myv65 has an article on this tubing issue, and he recommends using one size larger than the blocks inner channel size equivalent, or something like that...

Stepback · 10-01-2002, 09:11 AM

Y'all got me confused. What I was taught in school, the english system or SAE if you like, goes like this.

1/8, 1/4, 3/8, 1/2, 9/16, 5/8, etc ....

1/2 = 4/8

So wouldn't that make 1/2 larger than 3/8. Call me dumb, but reading this thread makes no since to me. Why you would want 3/8 barbs or 3/8 anything for that matter?

bigben2k · 10-01-2002, 09:57 AM

He he...

Here's a quote:
"For maximum performance: Look for a pump rated in excess of 300 gph with 1/2” fittings. Match the remaining components accordingly so that true system flow is at least 90 gph. The flow path through the water block should be roughly .06 inches^2 (equivalent to about 0.3” diameter or about 1/4” by 1/4”) to maximize convection. "

The article can be found here

gmat · 10-01-2002, 10:59 AM

First, let me clarify one point: 3/8" barbs = 8/10mm ID/OD (assuming 1mm walls), 1/2" barbs=10/12mm.
Then 1048 has both inlet and outlet in 1/2" = 10/12mm.
DD blocks comply to these specs.

Next, i think my pump is slightly cavitating. I have a parasite noise ("bzzzt") only when the pump is under load (ie in my PC). No such noise when the pump is free (ie in the kitchen sink).
The question is: should i port my pump inlet to prevent cavitation ?

myv65 · 10-01-2002, 03:06 PM

Quote:

Originally posted by bigben2k
myv65 has an article on this tubing issue, and he recommends using one size larger than the blocks inner channel size equivalent, or something like that...

Oh really? I guess I'll have to go find it and read it sometime as it sounds very informative. LOL. Nah, I haven't gotten that far, yet.

In the meantime, I rely on www.mcmaster.com for dimensional information about any fitting you can imagine. It takes quite a few clicks, but they have 2-D and 3-D images of all the fittings they offer.

As to the general reason why suction lines are larger than discharge lines, it has to do with velocity and pressure. If suction pressure gets too low, you'll have cavitation. Suction pressure is largely dependent on flow rate and area, which determines velocity. Lower the flow rate or increase the flow area, and velocity drops. As velocity drops, so to does vacuum level. So long as vacuum stays below ~15 in Hg, you should have no worries with cavitation.

[edit start]
Darn forum clock got screwed up during the server switch and wouldn't let me post a new reply because this one was posted "in the future".

Hey Ben,

Quote:

Originally posted by bigben2k
He he...

Here's a quote:
"For maximum performance: Look for a pump rated in excess of 300 gph with 1/2” fittings. Match the remaining components accordingly so that true system flow is at least 90 gph. The flow path through the water block should be roughly .06 inches^2 (equivalent to about 0.3” diameter or about 1/4” by 1/4”) to maximize convection. "

The article can be found here

Yeah, I kinda figured that's what you were referencing, but I was pretty sure it didn't say anything about going one size smaller.

Nice to know someone actually reads all the way to the end. . .

[edit end]

myv65 · 10-01-2002, 04:23 PM

Quote:

Originally posted by gmat
Next, i think my pump is slightly cavitating. I have a parasite noise ("bzzzt") only when the pump is under load (ie in my PC). No such noise when the pump is free (ie in the kitchen sink).
The question is: should i port my pump inlet to prevent cavitation ?

Are you certain it's cavitation? It could also be simple vibration of the pump. Two things you can do to verify.

1) When it's in the sink, gradually blind off the intake with your thumb. As you restrict flow, the pump will begin to cavitate. Don't completely blind off the intake and don't do this for an extended period as cavitation will eventually cause permanent damage. This will allow you to know positively what it sounds like when your pump cavitates.

2) When it's in the computer, unmount it and either hold it in your hand or put it on top of a folded up hand towel. This will tell you if the pump is causing something in the case to vibrate.

There are a few things that can solve the first, though not all are practical. Ultimately you need to either increase the suction pressure or decrease the flow velocity.

Increasing pressure) You can put a water column open to atmosphere on the suction side (T it into the normal flow line). This will put atmospheric plus the height of the column on the suction side. Honestly, this isn't practical and would only help if you were "just barely cavitating" as you can only make a column so high.

If you really want to get funky, you can add an accumulator to your system (closed-loop only). This raises overall pressure throughout the system. All this amounts to is a vessel (with an air fitting) that you partially fill with water. Once the entire system is closed, you pump a few psi into the vessel. Obviously this has the potential to cause leaks around connections if they aren't tightly sealed. You really don't need much air volume in the vessel. Be warned, though, that overpressurizing an accumulator will cause fittings to blow.

Decreasing velocity) You can open the suction line as you have proposed. You can also restrict the flowrate, which lowers velocity at the suction. I suspect this second alternative isn't very attractive.

MadDogMe · 10-02-2002, 03:43 AM

Quote:

Why you would want 3/8 barbs or 3/8 anything for that matter?

Who said anything about wanting 3/8Barbs?. I'd like 3/8 BSP threads on my block, as opposed to 1/4inch threads, so I could put 5/8 Barbs on it

...

************************************************** *********************

I'm certainly gonna port my 1250 out IF I can get hold of a 3/4Inch barb for the inlet, as well as the 5/8, (that I CAN get).

It won't be any time soon though!

,I'll do a thoroughly unscientific test when I do and let you know what gives

.
I'll do a 'fill the bucket test, before and after. also I'll do the same with some constrictive stuff(blocks & rad,ect) to see what it does under load...

09-30-2002, 04:33 AM	#1
MadDogMe Thermophile Join Date: Aug 2002 Location: Just shut up ;) ... Posts: 1,068	Tuning the Ehiem 1250?.... Has anyone tried tuning the inlet holes on the 1250?, they are very badly designed I think!, if getting more/faster water to the impellor is important, then definatly badly designed!!. I'm on about the 'peice' that the inlet barb screws into. it looks kinda like a ...., well I don't know what it looks like so lets call it the 'inlet housing'. it's the round peice with an 'O Ring' on it that clamps and seals onto the pump body with a 'ring~like' retension thingy with four stops on it . The inlet housing has qite a large bore but the part that lets water enter into the impellor is made of four small 'slots' around a 'cup' that holds the nylon centre spindle(of the impellor) in place. the bore of the housing actaly narrows down as it nears the 'slots'. These slots could be 'ported' or 'opened up' quite easily with a dremel or needle files. Has anyone ever done this?. I imagine you could easily double the area that water enters through without weakening the housing at all. I thought of using a peice of Cu(with hole for spindle, and doing away with the 'rubber gromet' thing) to 'bridge' across the gap instead of the 'too large' cup and rubber design. it would be alot more streamlined and less flow restrictive. The thing is I want to know whether this is important for flow, whether this is actualy restricting the water flow to the impellor. whether the impellor could shift more water, or wether this has been balanced in the design.(this I doubt considering the nature of the pumps intended usage. it would be easier to just make it bigger , more powerful than to tune it)...

09-30-2002, 05:06 AM	#8
MadDogMe Thermophile Join Date: Aug 2002 Location: Just shut up ;) ... Posts: 1,068	My 1250 has a 3/8 outlet!,I thought it was 1/2 at first cause my 1/2pipe fitted onto it perfectly, but it's definatly 3/8. If the inlet IS balanced at manufactur, it's balanced for a 3/8 outlet! . we'll have to port it and see what happens. I can't imagine it would do any harm, and you could always epoxy an 'original sized' thin plate back over the hole ... ************************************************ ******* PS. I don't understand how they come up with thread measurements, can you explain them?. is it to do with the amount of threads in a given 1/2inch. I read that the Maze3:1 I have has 1/4inck BSP thread, I'd like to understand exactly what it means :shrug: ... Ignorance is'nt always Bliss! ... Last edited by MadDogMe; 09-30-2002 at 05:12 AM.

09-30-2002, 04:56 PM	#11
decodeddiesel Cooling Savant Join Date: Oct 2001 Location: classified Posts: 534	hmm...never really thought about porting and polishing my pump before, but this sounds interesting __________________ ...i hurt... do me a favor, disconect me... they can re-work me but i'll never be top of the line again ...i'd rather be nothing...

10-01-2002, 08:59 AM	#19
bigben2k Responsible for 2% of all the posts here. Join Date: May 2002 Location: Texas, U.S.A. Posts: 8,302	I just picked up a Little Giant 2-MDQ-SC, and it has 1/2 fittings, in and out. I picked up CPVC fittings at Lowes, and a good 1/2 barb with 11.5mm ID at Home Depot. Lowes sells cheap 1/2 barbs that are seriously undersized. myv65 has an article on this tubing issue, and he recommends using one size larger than the blocks inner channel size equivalent, or something like that... __________________ WBTA (Water Block Testing Alliance) Nordic Hardware WC 101

10-01-2002, 09:11 AM	#20
Stepback Cooling Neophyte Join Date: Feb 2002 Location: Houston Texas Posts: 52	Y'all got me confused. What I was taught in school, the english system or SAE if you like, goes like this. 1/8, 1/4, 3/8, 1/2, 9/16, 5/8, etc .... 1/2 = 4/8 So wouldn't that make 1/2 larger than 3/8. Call me dumb, but reading this thread makes no since to me. Why you would want 3/8 barbs or 3/8 anything for that matter? __________________ Stepback Maintaining today for a better tommorrow.

09-30-2002, 04:41 AM	#2
Cathar Thermophile Join Date: Sep 2002 Location: Melbourne, Australia Posts: 2,538	If you think the 1250 is scary, take a look at a 1048 some time. The shape is kinda like a radiation hazard symbol is how I would describe it. I've often pondered just the same thing, about widening the holes.

09-30-2002, 04:47 AM	#3
Cathar Thermophile Join Date: Sep 2002 Location: Melbourne, Australia Posts: 2,538	Just pulled my 1250 apart and took a closer look. The radius of the greater inlet size is 16mm. The radius of the spindle holder is 11mm. The 3 structs that hold the middle in place are 2.5mm x 2mm. This gives a total intake area of: 201 - 95 - 15 = 91mm^2 The ID of the stock 1/2" outlet barb is 10.5mm, or 86.6mm^2. So basically the inlet holes are less restrictive to the pump than the outlet 1/2" barb.

09-30-2002, 05:01 AM	#6
MadDogMe Thermophile Join Date: Aug 2002 Location: Just shut up ;) ... Posts: 1,068	Another question!, is the outlet the same (standard?) thread as a 1/2inch barb?(1/4BSP~thread?), or is it metric?...

09-30-2002, 05:04 AM	#7
Cathar Thermophile Join Date: Sep 2002 Location: Melbourne, Australia Posts: 2,538	The outlet barb uses 3/8" BSP thread. The inlet 1/2" BSP. I replaced my inlet and outlet barbs with brass barbs.

09-30-2002, 05:18 AM	#9
Cathar Thermophile Join Date: Sep 2002 Location: Melbourne, Australia Posts: 2,538	I don't pretend to understand why, but the maximum barb size for a particular BSP thread is 1/4" larger than the thread size given. For example, a 1/4" BSP thread will allow for a 1/2" barb size with no flow restriction. A 3/8" thread will allow for a 5/8" barb size, and so on. Go figure. I didn't invent the standard. In other words, the Eheim 1250 has a 3/8" BSP thread with a 1/2" barb on it. However, if one so wishes, they can stick a 3/8" thread - 5/8" barb on it.

09-30-2002, 05:28 AM	#10
MadDogMe Thermophile Join Date: Aug 2002 Location: Just shut up ;) ... Posts: 1,068	Excelent!, OCPC sell the larger 5/8 (14mm~internal?) barb, I'll have to replace the 3/8 outlet with one. and maybe a 3/4 for the inlet?. definatly have to port the holes then ...

10-01-2002, 01:14 AM	#14
Cathar Thermophile Join Date: Sep 2002 Location: Melbourne, Australia Posts: 2,538	I was looking at the Eheim 1250 manual that was sitting on my box. Who do I trust more? The Eheim manual, or Danger Den possibly mis-typing something. The Eheim 1250 inlet is a 5/8" barb. You just have to look at the pump and you know that the inlet is larger than the outlet. If DangerDen are saying 3/8" inlet and 1/2" outlet, then they have a type on their page and should correct it.

10-01-2002, 04:44 AM	#17
MadDogMe Thermophile Join Date: Aug 2002 Location: Just shut up ;) ... Posts: 1,068	Cathar!, sorry, you're right. I always took a 1/2inch barb to mean 12mm inner, they're not!. the outside diametre of my maze3;1 '1/2inch' barbs is'nt even 1/2inch!!. So a 1/2 barb is 12mm outer diametre, with a 10mm inner. It gets confusing seeing 3/8tube advertised as 10mm inner. so infact 1/2inch barbs would be better fitted with 3/8Tube!!, at least the flow would be constant: 10mm > 10mm, Looney!! ... ************************************************ ***************** Seeing this I can understand why the block is 'so' restrictive, it really needs a 12mm inner diametre barb to utilize the full flow . The first block I make will definatly use 3/8 thread!!. why are'nt the manufacturers doing this! :shrug: , Crazy!...

10-01-2002, 09:57 AM	#21
bigben2k Responsible for 2% of all the posts here. Join Date: May 2002 Location: Texas, U.S.A. Posts: 8,302	He he... Here's a quote: "For maximum performance: Look for a pump rated in excess of 300 gph with 1/2” fittings. Match the remaining components accordingly so that true system flow is at least 90 gph. The flow path through the water block should be roughly .06 inches^2 (equivalent to about 0.3” diameter or about 1/4” by 1/4”) to maximize convection. " The article can be found here __________________ WBTA (Water Block Testing Alliance) Nordic Hardware WC 101

10-01-2002, 10:59 AM	#22
gmat Thermophile Join Date: Mar 2001 Location: France Posts: 1,221	First, let me clarify one point: 3/8" barbs = 8/10mm ID/OD (assuming 1mm walls), 1/2" barbs=10/12mm. Then 1048 has both inlet and outlet in 1/2" = 10/12mm. DD blocks comply to these specs. Next, i think my pump is slightly cavitating. I have a parasite noise ("bzzzt") only when the pump is under load (ie in my PC). No such noise when the pump is free (ie in the kitchen sink). The question is: should i port my pump inlet to prevent cavitation ?

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