Stuart Chignell wrote:
So if I wee to aim fire water velocities of between 75cm/s and 100cm/s you should be right.
Sorry Stuart, couldn't resist having a giggle at that typo...
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| Pipe sizing and losses http://byap.backyardmagazines.com/forum/viewtopic.php?f=12&t=12991 |
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| Author: | Greenhomesteader [ Jun 21st, '12, 10:28 ] |
| Post subject: | Pipe sizing and losses |
I haven't done much plumbing design, so I have a few questions. 1) Is there a rule of thumb for pipe size? I would think something along the lines of: (Volumetric Flow rate) X (?? constant) = (minimum pipe diameter) This would be lower diameter for a pressurized line from a pump than for a gravity fed line such as a GB drain pipe. 2) Is there any rule of thumb for added head loss due to 90 degree turns in the piping. 3) Is there any benefits or drawbacks to CPVC fittings versus standard PVC? 4) If I use a threaded coupling, do I need to use teflon tape like a compressed air line? Thanks, GH |
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| Author: | bunson [ Jun 21st, '12, 10:47 ] |
| Post subject: | Re: Pipe sizing and losses |
Try this website for numbers in imperial measurements : http://mobile.engineeringtoolbox.com/pvc-pipes-equivalent-length-fittings-d_801.html although these are general and may be different from those provided by your pipe manufacturer. PVC and CPVC have the same roughness so in theory should the same flow, discounting expansion/compression etc. Thread tape isn't really required, but if you fear leaks you can use a little tape, a smear of silicon or Vaseline. |
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| Author: | Stuart Chignell [ Jun 21st, '12, 13:51 ] |
| Post subject: | Re: Pipe sizing and losses |
A rule of thumb I work to is to keep the water velocity under 1m/s For drains I want to make sure it is not too low our you will get sedimentation in the drain. The bigger the pipe the faster you need it to be flowing in order too keep things moving. For 100mm pipes I think it is around 65cm/s. So if I wee to aim fire water velocities of between 75cm/s and 100cm/s you should be right. |
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| Author: | earthbound [ Jun 21st, '12, 15:56 ] |
| Post subject: | Re: Pipe sizing and losses |
Stuart Chignell wrote: So if I wee to aim fire water velocities of between 75cm/s and 100cm/s you should be right. Sorry Stuart, couldn't resist having a giggle at that typo... |
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| Author: | Stuart Chignell [ Jun 21st, '12, 16:00 ] |
| Post subject: | Re: Pipe sizing and losses |
My excuses are bureaucratic induced stress and using my phone while waiting for lunch at 4:00pm. |
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| Author: | Stuart Chignell [ Jun 21st, '12, 16:01 ] |
| Post subject: | Re: Pipe sizing and losses |
earthbound wrote: Stuart Chignell wrote: So if I wee to aim fire water velocities of between 75cm/s and 100cm/s you should be right. Sorry Stuart, couldn't resist having a giggle at that typo... That should read: So if I were you I would aim for water velocities of between 75cm/s and 100cm/s. |
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| Author: | bunson [ Jun 21st, '12, 16:21 ] |
| Post subject: | Re: Pipe sizing and losses |
I like to have the drain moving as fast as possible which allows for adding venturis or hard splashing for aeration, or swirling the FT. |
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| Author: | Stuart Chignell [ Jun 21st, '12, 16:39 ] |
| Post subject: | Re: Pipe sizing and losses |
First high velocity anywhere in your system means extra electricity. Friction loss is proportional to the square of the velocity. Small increase in velocity means big increase in friction and consequently greater dynamic head. So either more electricity is needed to get a desired result or you will get less flow from a specific pump. I don't believe that you can practically get venturis and such on drains without considerable fall which means a lot of extra electricity from pumping the water back up to where it originally came from. The faster the water in the drains moves the greater the chance that the solids will get broken up and be harder for the filters to catch. |
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| Author: | earthbound [ Jun 21st, '12, 16:45 ] |
| Post subject: | Re: Pipe sizing and losses |
I like it, should be more interesting typos like that..... 
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| Author: | Stuart Chignell [ Jun 21st, '12, 16:57 ] |
| Post subject: | Re: Pipe sizing and losses |
I do lots of them but generally I check before I post. |
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| Author: | bunson [ Jun 21st, '12, 17:18 ] |
| Post subject: | Re: Pipe sizing and losses |
Stuart Chignell wrote: I don't believe that you can practically get venturis and such on drains without considerable fall which means a lot of extra electricity from pumping the water back up to where it originally came from. I disagree. Stuart Chignell wrote: The faster the water in the drains moves the greater the chance that the solids will get broken up and be harder for the filters to catch. Drains are the outflows from the GB where any solids have already been filtered by moving the water slowly through the media. |
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| Author: | Greenhomesteader [ Jun 21st, '12, 21:23 ] |
| Post subject: | Re: Pipe sizing and losses |
Stuart Chignell wrote: The faster the water in the drains moves the greater the chance that the solids will get broken up and be harder for the filters to catch. That's what I was thinking too, but if it's too slow, you would get more settling in the pipes. Edit: Oops, you said that happens at 65cm/s, I missed it. |
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| Author: | Stuart Chignell [ Jun 22nd, '12, 05:16 ] |
| Post subject: | Re: Pipe sizing and losses |
@greenhomesteader it depends on the pipe size bigger pipes need to be moving faster. The formula is U=sqrt(9.81 x d) x 0.58 Where U equals velocity and d equals the internal pipe diameter. @Bunsun I wouldn't have the pump in the FT so that it did not chop up the solids. The discussion has been had on other threads and is less relevant for backyard systems but I would still have the pump in the sump. How big a fall is creating that air flow and what is the configuration of the plumbing to get the air into the pipe? |
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| Author: | bunson [ Jun 22nd, '12, 08:52 ] |
| Post subject: | Re: Pipe sizing and losses |
Stuart Chignell wrote: How big a fall is creating that air flow and what is the configuration of the plumbing to get the air into the pipe? http://www.backyardaquaponics.com/forum/viewtopic.php?p=328174#p328174 Scott |
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| Author: | Greenhomesteader [ Jun 22nd, '12, 10:32 ] |
| Post subject: | Re: Pipe sizing and losses |
Stuart Chignell wrote: @greenhomesteader it depends on the pipe size bigger pipes need to be moving faster. The formula is U=sqrt(9.81 x d) x 0.58 Where U equals velocity and d equals the internal pipe diameter. I'm assuming those are SI units. |
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