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Siphon Draining Too Slow
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Author:  Kenn [ Jan 13th, '14, 10:14 ]
Post subject:  Siphon Draining Too Slow
Have a 1000L FT, with a 8x4x1 GB with grow media, flowing into another 8x4x1 GB DWC that pumps back to the FT. My siphon fires right away and the outpipe is 1" from the GB to the DWC. My pump is pretty aggressive which I thought would be good but my problem is that the GB takes over 20 minutes to drain even though the water is flowing pretty strongly. Is my only option to make the drainage pipe larger or is there something else I should consider.

Also how long is the ideal time to drain a bed?
Author:  Slowboat [ Jan 13th, '14, 10:22 ]
Post subject:  Re: Siphon Draining Too Slow
Can you divert some of the pump water back into the FT thus slowing the flow to the GB?

This will also give some extra aeration to the water in FT.
Author:  earthbound [ Jan 13th, '14, 10:35 ]
Post subject:  Re: Siphon Draining Too Slow
Why is it a problem?

Apart from the fact that your probably using way more power than what you need..
Author:  Mr Damage [ Jan 13th, '14, 11:41 ]
Post subject:  Re: Siphon Draining Too Slow
Kenn wrote:
Have a 1000L FT, with a 8x4x1 GB with grow media, flowing into another 8x4x1 GB DWC that pumps back to the FT. My siphon fires right away and the outpipe is 1" from the GB to the DWC. My pump is pretty aggressive which I thought would be good but my problem is that the GB takes over 20 minutes to drain even though the water is flowing pretty strongly. Is my only option to make the drainage pipe larger or is there something else I should consider.

Also how long is the ideal time to drain a bed?
If you're talking a total flood and drain cycle time of 20 minutes, then that's fine.

If you're talking about a drain time alone of 20 minutes, then something isn't right.

Doing the maths on your GB you have a smidge over 900L total gravel capacity, so when flooded to about 250-260mm depth it would contain about 300L of water... รท 20 minutes = 15L per minute coming through your siphon, or 250ml per second... a 25mm (1") siphon should flow way more than that at full flow. My 20mm siphon flows 400ml per second, so over 20 mins would flow 480L

Is there enough holes/slots in the outer gravel guard and are the holes/slots in the bell sufficient to allow maximum water flow through the 25mm standpipe?
Author:  Kenn [ Jan 27th, '14, 09:24 ]
Post subject:  Re: Siphon Draining Too Slow
Slowboat - Not sure I can divert water back to the FT - the only possibility would be diverting some of it back to the DWC that the pump is in.

Earthbound - Not sure if it was a problem that was my original question :)

Mr Damage - It appears that its firing at full speed as the drainage pipe has a full stream of water coming out just feeling like maybe my bed is too large being 8FT x 4FT x1FT for a one inch drain pipe or do you think the one inch is fine for that size? Seems like people might usually have one every 4ft x 4ft. I was thinking about bumping it up to 1.5in instead. The slots in the media gard are quite extensive and I think definitely allow for enough flow. Maybe my bell isn't large enough - its 2" and the stand pipe is 1".

So with all of that I basically have three questions.

1. Should I make the 1" drain pipe wider and replace it with a 1.5" drain pipe to help it drain quicker
2. Should I make the actual bell larger instead of 2"
3. I currently added a valve to the pipe coming off the pump to slow down the water flow - is that the appropriate place to add it or is that really bad on the pump?

Thanks!
Author:  Kenn [ Feb 2nd, '14, 03:46 ]
Post subject:  Re: Siphon Draining Too Slow
Just wanted to follow up and see if anyone had insights into these three questions:

1. Should I make the 1" drain pipe wider and replace it with a 1.5" drain pipe to help it drain quicker
2. Should I make the actual bell larger instead of 2.5"
3. I currently added a valve to the pipe coming off the pump to slow down the water flow - is that the appropriate place to add it or is that really bad on the pump?
Author:  Stuart Chignell [ Feb 2nd, '14, 04:52 ]
Post subject:  Re: Siphon Draining Too Slow
This might not be possible but a siphon will drain a lot faster if you can extent the vertical fall of the pipe.

Same as with a drain.

If you have a bath up on a stand but with nothing connected to the drain it will empty relatively slowly. If you connect a pipe from the bath drain down to the ground then the bath fill empty much faster.

If you had a diagram it might be easier to give more advice.
Author:  Kenn [ Feb 2nd, '14, 05:39 ]
Post subject:  Re: Siphon Draining Too Slow
Biggest question is that I have a 1" drain pipe, and my bell is 2.5" - the more I look it seems like people are using much larger bells so my thought is that I should bump up my bell to 4" wide or something much wider and that might make it drain much quicker. Is that correct? What is the recommended bell size on a 1" drain pipe?

Second question in the thread that I was still hoping to get answered is if its bad for my pump that I am limiting how much it can pump by placing a valve on the out pipe to slow it down a bit to create the right flow for my siphon?
Author:  Stuart Chignell [ Feb 2nd, '14, 05:52 ]
Post subject:  Re: Siphon Draining Too Slow
Kenn wrote:
Biggest question is that I have a 1" drain pipe, and my bell is 2.5" - the more I look it seems like people are using much larger bells so my thought is that I should bump up my bell to 4" wide or something much wider and that might make it drain much quicker. Is that correct? What is the recommended bell size on a 1" drain pipe?

Second question in the thread that I was still hoping to get answered is if its bad for my pump that I am limiting how much it can pump by placing a valve on the out pipe to slow it down a bit to create the right flow for my siphon?


In answer to the second question the answer is no within reason for centrifugal pumps (almost all pond pumps are centrifugal except for a few really expensive ones).

I'd be more concerned that your 1" drain is too small.
Author:  Stuart Chignell [ Feb 2nd, '14, 05:56 ]
Post subject:  Re: Siphon Draining Too Slow
Pictures and diagrams make things easier.

Going back through the thread I'm with EB. Do you actually have a problem? If it takes 20min to drain and the siphon stops what is the problem?
Author:  Kenn [ Feb 2nd, '14, 06:36 ]
Post subject:  Re: Siphon Draining Too Slow
It doesnt always stop and its taking 20 minutes to drain. If it could drain quicker I could potentially let it fill quicker - opening my pump up a bit, circulating the water better, and draining the bed quicker.

Seems that most people have a very large bell - which has continued to be my same question - what is the recommended bell width for a 1 in drain? :)
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