bioaquafarm wrote:
I think you are right about the low pressure from AP valves, I do not remember now the minimum flow requirement for my spring disk but surely must handle more than a 5000lt x hr pump!
It may... it quite possibly wont though....
The product has been primarily designed to work with pressure.... and high flow rates....
The "optional" extras.. were designed to make the product adaptable to rainwater pump irrigation systems....
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While your preference clearly tends toward FIMCO, I personally prefer the sturdy construction of KRAIN (cast iron body) as the flow I'm using and the pump give a certain pressure shock every time the pumps goes on! as you have suspected there is quite some pressure in a 20000lt pump with a 10m head.
A plastic case will degrade faster than cast iron! specially in a hot environment like a GH.
The metal die cast body is certainly probably preferable in high pressure irrigation systems...
But like the Fimco irrigation valves... and the aquaponics valve.... the Krain still uses ABS polymer plastics for most of the unit...
I'm still using the original prototype aquaponics valves... since modified, and improved with UV stabilised/resistant components.... and they've been totally exposed to outside weather and sunlight for five years...
And I think I can comfortably say that our temperature and UV extremes far exceed anything you might be likely to encounter... or most other potential client locations...

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Out of curiosity.. does the FIMCO AP index valve have a pressure relieves valve so the disk does not get stuck under water backpressure suction?
As far as I know... the Fimco irrigation valve doesn't have a pressure relief valve... I could be wrong....
But neither does the Krain.... it has a vacuum release....
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Built-In Atmospheric Vacuum Breaker-Releases any vacuum created between the pump and the valve on shut-down.
The aquaponcis valve is not designed for... or used in very high pressure situations... and just simply would not encounter any "backpressure suction"...
The vacuum release system you refer to on the Krain product... is utilised in high pressure/high flow primed pump situations.... (usually inline pumps)...
Virtually nobody in a backyard aquaponics system would be running inline pumps... and those that might are unlikely to be running high volume/pressure primed pumps...