Question for the plumbers - The Planted Tank Forum
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post #1 of 22 (permalink) Old 12-15-2014, 04:18 PM Thread Starter
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Question for the plumbers

I'm going to change my filter bendy pipes into actual PVC plumbing (Push fit) at the moment there are no 90 bends, but when I change it over there will be about 8 90 bends in it, what will this do to the flow?
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post #2 of 22 (permalink) Old 12-15-2014, 04:33 PM
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Slow it down. How much, who knows?
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post #3 of 22 (permalink) Old 12-15-2014, 04:57 PM
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Slow it down and you may hear some turbulence through it depending one how fast you're pushing water.

Gotta ask why Push fit though?

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post #4 of 22 (permalink) Old 12-15-2014, 05:15 PM Thread Starter
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Slow it down and you may hear some turbulence through it depending one how fast you're pushing water.

Gotta ask why Push fit though?
Easy cheap and quick! Will there be a drastic reduction in flow? Its just at the moment I can't close my cupboard door because the filter and pipes don't even fit, its either this or build a new cabinet.
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post #5 of 22 (permalink) Old 12-15-2014, 06:02 PM
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It only takes seconds and not much money to glue PVC or CPVC. I'm not sure what's available in the UK. A push fit should be a quick and dirty, temporary, "see if it works" solution. If it works itself loose, you'll wish you did it differently............I did.

As Vancat2 noted, there's no way to tell how much until you try it.

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post #6 of 22 (permalink) Old 12-15-2014, 06:07 PM
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Going from zero to eight 90 degree bends is...a lot. I'd say there will be a drastic flow reduction, and possibly some noise. But as others have said, just have to try it and see exactly how much.


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post #7 of 22 (permalink) Old 12-15-2014, 06:43 PM
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Quote:
Originally Posted by AshNeon93 View Post
I'm going to change my filter bendy pipes into actual PVC plumbing (Push fit) at the moment there are no 90 bends, but when I change it over there will be about 8 90 bends in it, what will this do to the flow?
Hi Ashneon,

The insertion of a 90 degree elbow in 1/2" line tubing is approximately the same as adding 9.4 feet to the length of the tubing. Adding 10 such elbows will be the equivalent of adding approximately 94 feet to your tubing length with the resulting drop in flow.

How much the flow drops depends upon your current tubing length but lets say your current tubing is 10 feet. With 10 of the 90 degree elbows added your equivalent tubing length will be about 100 feet. According to what I remember from physics if the length is doubled the flow is halved. So lets do some quick and dirty math to estimate your flow. Let's say your current flow is 300 gallons per hour with your 10 feet of tubing. The addition of 10 of the 90 degree elbows would result in a flow of approximately:

10' = 300 gph
20' = 150 gph
40' = 75 gph
80' = 37 gph
100' = 28 gph (approx)

Please note that the calculations above are theoretical; your actual results may vary but if it were me I would look for other alternatives.

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post #8 of 22 (permalink) Old 12-15-2014, 06:55 PM
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On partial fix is go up a size relative to the tubing. Bigger pipe reduces friction significantly, and will help make up for 90's.

Also, look and see if can do 45's instead of 90's in some places, e.g. going over a hump can be done with four 90's, but if you have lateral space you can do four 45's and go up with a slope. This is particularly true going down into the tank, e.g. to a spray bar.

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post #9 of 22 (permalink) Old 12-15-2014, 06:55 PM
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I was in irrigation repair for 18 yrs and for every 90' bend there is a half pound loss. So if you have a pump that has 5-10 lbs output you see how that many elbows will do to the flow.
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post #10 of 22 (permalink) Old 12-15-2014, 07:36 PM Thread Starter
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Oh right so it seems to be there is a massive loss and I'm using a Eheim eco pro 130 on a 26g so I don't have that much play, looks like a new cupboard it is! I would of preferred to do the pipe and if I do still do the pipe I won't do it push fit, thanks for all your tips and theory's people I appreciate it.
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post #11 of 22 (permalink) Old 12-15-2014, 07:51 PM
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There have been studies using short bend 90* (typically found in plumbing and irrigation), long bend 90* (available for some types of pipe) and using 2 x 45* fittings to make a sort of long bend 90*.

The short bend 90* was the worst.
The long bend 90* was the best.
The 2 x 45* was very good. Not quite as good as the long bend 90*, but close. Worth the extra price over the short bend 90*.

Note that these tests were done with much larger pipe (3-4"?) But the concept is the same. The less changes of directions, and the smoother the change the better.
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post #12 of 22 (permalink) Old 12-15-2014, 07:56 PM
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I think you should get a new cabinet.
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post #13 of 22 (permalink) Old 12-15-2014, 08:02 PM
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Bear in mind some of the answers you are getting are likely based on a lot higher flow rate and pressure than used in a typical canister filter. Friction loss goes up with the SQUARE of the velocity, so twice the flow means 4 times the friction. So loss from (say) house water supply or sprinkler systems is a lot different than a low flow circulation pump.

I'm not saying it is not an issue, I think you might be very surprised. I just looked and my plumbed tank has three 90's on the intake, and five on each outflow (except one of the three has 2 45's vs 2 90's). That's a lot of turns, but honestly I do not see a noticeable drop in outflow vs. when I tested it in a sink with buckets. I'm sure there is some, but it was perfectly acceptable, and a LOT easier than using flexible tubes.

As mentioned -- PVC is cheap. It's no big deal to test, and I suspect you will find it works just fine.

But if flexible works for you, great.

Here's where my 90's went. This is looking UP toward the top of a 6' tank. Two canisters each go along each side to the two center braces as a spray bar, and the third is on the far right on this photo.



By using PVC everything is stationary and doesn't flop around.



This is a top view where they all go into the tank. Despite all that pipe, there's a small cover over one end, and no one notices the plumbing when looking at the tank.

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post #14 of 22 (permalink) Old 12-16-2014, 12:17 AM
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Why not just go with flex pipe aka spa tubing. I ordered 1/2",3/4" and 1" all from Amazon for about $50 a roll. Sure its a bit expensive but much less restrictive. I used it on the project from my signature and it really cuts down on elbows in tight spaces when you want to avoid restricting flow. It glues into sch. 40 and 80 fine. Just don't use primer. Find Christy's pvc glue and it will work like a charm.

I agree with going up a size to minimize fiction loss. This will come at a price for it will take up much more space though.

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post #15 of 22 (permalink) Old 12-16-2014, 12:17 PM
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Quote:
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Why not just go with flex pipe aka spa tubing. I ordered 1/2",3/4" and 1" all from Amazon for about $50 a roll. Sure its a bit expensive but much less restrictive. I used it on the project from my signature and it really cuts down on elbows in tight spaces when you want to avoid restricting flow. It glues into sch. 40 and 80 fine. Just don't use primer. Find Christy's pvc glue and it will work like a charm.

I agree with going up a size to minimize fiction loss. This will come at a price for it will take up much more space though.

When I re-read the initial post, I realized I missed the part about 8 90's. The light bulb flickered in my head and I could see a use for Spaflex. You should be able to cut out a lot of those 90's using it as flight50 also suggested. An alternative would be to terminate your PVC connections with threaded adapters and attach grey barbed fittings that accept vinyl hose (black if you can find it). This may give you some more flexibility in the even something needs to change down the line, but Spaflex would be the ideal solution.

Angelo

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