first proposition is without sump,
which automatically means you locate the pump(s) either in the fish tank or in the growbed(s), NOT in the nonexistent sump.
Exactly what I said...
Which means that you have to gravity drain your growbeds back to the fish tank... which means raising them above the fish tank or lowering the fish tank by digging it in...
let's suppose the pump(s) is(are) in the fish tank (which I believe is the traditional way, and I would second that):
if the growbeds are then equipped with just a standpipe with a drain hole (smaller than the pump's output) at the bottom of it and an overflow, then timing the pump that leads to this particular growbed would be easy.
Exact timing would not be necessary: as long as the overflow level is reached, this would be OK.
frequency of flooding remains very possible.
Probably true Frank, and only differs slightly from the normally adopted, tried and tested method, where there are many holes drilled in the outer cover pipe and a single hole in the bottom of the standpipe... drainage begins immediately, overflows the standpipe, and continues after the timer ceases the pump through the bottom hole in the standpipe.
Setting the height of the standpipe correctly acts as the overflow... setting the timer to 15on/45off is suggested because many timers only have 15 min interval set points...
And 45 mins off has been shown to provide sufficient time to drain and sufficient oxygenation... but it assumes a sump concept with a pump (usually float activated) in the sump...
locating the pumps in the growbeds is more problematic so I will not go into it.
I hadn't even interpreted your design as actually involving pumps in the growbed... I'm not sure what possible benefit this concept would acheive... and it would take up further room in the growbed that could be utilised by plants...
Further you would then have to deal with the inevitable invasive roots blocking the pump(s)...
it is quite obvious that 2 and 4 pumps are more costly than one.
but inefficient ??? why would that be ???
... please explain ...
Four pumps means four times the electrical consumption... granted your could size the pumps down and possibly acheive the same or even slightly less consumption ...
where system security is concerned:
4 pumps each stand a chance of breaking down, which is obviously more than one pump, I will grant you that
this doesn't however increase the chance of a general system breakdown by a factor of 4.
If each bed is supplied by a single pump.... and a pump fails then you have a system breakdown... compromise the plants at the very least....
A single pump is perhaps just as likely to breakdown, and similarly compromise the system... but IMO is more likely to be recognised and acted upon... whereas 1 pump failure amongst 4 pumps may go un-noticed...
The likelyhood of 4 pumps simultaneously breaking down would be (I estimate) 4^4 th = 256 times less than 1 pump breaking down, so you stand 256 times less the risk of losing your fish.
NOT 4 times more.
I never suggested that four pumps would breakdown simultaneously
just raised the point about one...
but lets assume that to be the case... i.e that a power failure has occured for instance... with each bed fed by a pump.... how would you organise a backup system that could supply all four beds and maintain bio-filtration and oxygenation??
As for the plants: it takes a lot of time for a growbed to go dry
unless your media has no water holding capacities whatsoever.
If your growbed can't stand say 12 hours between floods (ample time to replace a pump, and MUCH more time than droughts can occur in nature), I believe one should reconsider their growing media (i.e. mix some media with water holding capacities with it).
True the media will stay moist for some time... but remember that this is a constantly draining standpipe arrangement... and IMO it would be possible to not notice that one of the four pumps was inoperable... as the rest of the system would indicate that everything was operating as normal...
In this above described setup (with an overflow on each growbed standup pipe) the possibility of draining the fish tank is nonexistent (if need be I can explain further).
Incorporating an overflow (which you hadn't previously suggested
) would actually INCREASE the likelyhood of this occurring if a blockage occurred in a growbed drain as the fish tank pump(s) would continue to pump and overflow the growbed...
If the sump pump failed... as the pump... or 4 pumps would continue to feed to the growbeds and drain you would overflow the sump
yes, 4 pumps will probably be more expensive than only one
but TMHO the many advantages by far outweigh that.
Sorry but I can't really see any advantages at all...
And it would make harvesting your fish more difficult....
next: the sump tank variation does NOT include 4 pumps in the fish tank (don't mix up the solutions described).
please reread my post.
it incorporates a sequencer for flooding/draining the growbeds.
Sorry Frank if I mis-interpreted your idea... noted the point about "sequenced" growbeds, but nothing as to where the pumps would be located... assumed they would be in the fish tank as you didn't state otherwise... and everything suggested the pumps were in the fish tank...
if you would have 2 small pumps instead of one big one, timed alternately, each tubed to two growbeds
you would be left with 400 l in the fish tank
if you would have 4 small pumps instead of one big one, timed alternately, each tubed to one growbed
you would be left with 800 l in the fish tank
Where would you locate them? in the sump??
sure, a "one pump" system is simpler, but is it also "best"?
and even "cheaper"?
and more "reliable"?
"Best" ... there's no "set in stone" way to do things... but some ways have been proven to work, reliably... and to be easily implemented at minimal cost..
"Cheaper" .... noted that multiple pumps could be downsized and possibly consume less power and may be "individually" cheaper than a single pump...
But combined cost.... ??? ... then there's the additional costs involved with plumbed each growbed to each pump...
Cheaper... doubtful IMO...
don't forget: in a 1000 liter FT + 4 x 500 liter growbeds system and a "worst case scenario" without sump you are left with only 200 liter in the fish tank, and in a system with sump you need much more sump capacity = more footprint, higher cost.
Assumes a gravity feed growbed drainage... every other of your design options seems to suggest/incorporate a sump....
even if the cost of a bigger sump is less than the costs of the extra pumps, you will miss all the other advantages.
we are not talking here of irresponsible experiments, as we are not touching any of the basic principles of AP.
Never suggested the idea was an "irresponsible" experiment... doubt that any experiment (ethical anyway) is irresponsible...
Just suggested that as a new user
... it was perhaps best to start with proven, reliable design principles... and experiment later, if so desired ...
only of very arguable alternatives which will enhance a system and make it more reliable
as shown above
An assumption made by yourself... but not actually supported or verified by anyone to my knowledge... even yourself, to my knowledge have never actually built and operated such a system...