Backyard Aquaponics
A place to discuss aquaponics

What about keeping the guard the same size, but use 3/4 inch instead of 1" outlets? Keen to know the answer, as I'm going to cut up my blue barrel once the shed floor is down, storage shed emptied, gardens done, verge turfed (artificial again) ... oh shit, then cricket season will be upon us.

speed at which a grow bed (with a timed flood and drain type stand pipe) will flood is a function of the rate the water flows in and the size of the drain holes. If you only have a trickle of water coming in, it might be hard to flood the bed if the holes in the stand pipe are too big. The actual size of the stand pipe for a timed flood and drain bed doesn't matter all that much except that you want to make sure it is big enough that the bed can't "overflow".

If doing siphons the size of the siphon has to be appropriate for the inflow to the bed so that the siphon will work properly.

Hi TCLynx, i agree with you that it is the hole in the side of the standpipe not the size of the standpipe itself that determines the drain time for a given inflow.
the way i see it is where the hole in the side of the standpipe where the water leaves the growbed is the same size in the 600l growbed and the 100l blue barrel, the volume of water leaving over a given period is the largely the same so the barrels drain faster. i have a 8000l/hr pump that only just fills the 2 x 600l growbeds and 6 x 100l barrels in 15 mins. the water flowing to the barrels is considerably more than to the 2 growbeds even though the 6 barrels are equivalent in volume to one growbed. my concern with the extra water they recieve is that they will get proportionaly more solids and so may lead to problems in the future.

Reducing the amount of water entering the blue barrels must be offset by reducing the drain hole size if you want them to fill. if the hole is too small there is an increased capacity for blockage. therefore the question on the size of the drain hole in the standpipe in a blue barrel.

So far I've never experienced a problematic solids build up in a grow bed that was getting timed flow for flood and drain so what I would probably recommend is that you make sure you keep the stand pipe removable so in case you need to adjust the flow rates and hole sizes you can at a later date but I would probably not worry about it too much and just make it similar to your other beds.

The only beds I've so far had a "solids build up problem in" has been in beds that get a very large amount of flow, constantly.

I've come to the same conclusion TCL.... the build up in a constantly flooded grow bed... occurs much more rapidly than in a timed flood & drain from my experience...

Yep Rupe, and a siphon flood and drain bed might have a little build up but depending on the siphon size and flow rate, it is usually solved by poking with a stick.

Hi TCLynx can you elaborate some more on how the build up of solids are solved by poking with a stick or were you referring to something else.

If your water is entering the bed in just one point (like the corner of the bed) and that area starts to slime up so the water is spreading over the gravel some before it starts to drain down into the gravel. You can usually take care of that problem by stirring up the gravel in that area (poking it with a stick) so that you break up the bio-slime a bit and the water starts draining down into the gravel there again. Alternative might be to shift the spot where the water enters the bed for a while.

Or, don't have your water entering the bed at a single point... use a halo distribution around the grow bed...

And you wont have that problem...

Yea, instead you have to clean the grid weekly.

thanks for clearing that up
I have a cross shaped distribution on the blue barrels and a ring on the grow beds

I don't... doubtful if I even clean them monthly.... probably more like 6 monthly...

once a month or so i use a piece of wire to unblock any blocked holes.

I've only once ever installed a distrobution grid on a grow bed and that was for timed flood and drain getting fairly strong pump pressure.

I fear at the pressure I usually let water flow into constant flow beds (like for the siphon flood and drain beds or constant flood beds) that the distrobution grids would be constantly clogging and causing all sorts of problems seeing as all the constant flow or constant flood beds are getting gravity flow from the fish tanks in CHIFT PIST systems.

Heck even the spray bar on my fish tank really needs to be unclogged at least twice a month to the point that I finally added a free flow "snorkle pipe" on the end so that when the bar clogs up at least I will still get plenty of flow through the fish tank even if the spray bar is clogged. I cut slits in that pipe so I can use a log knife to unclog it since trying to poke gunk out of the holes was basically impossible while trying to reach the middle of a 1000 gallon fish tank.

If I am pumping to the bed doing timed flood and drain, then I've not had the slimming or clogging issue even with the water just entering the bed at one point so I don't see the benefit to adding the distrobution grid. Having the water enter in one spot actually makes it easier for me to dose things into the bed like chelated iron or seaweed extract since I can simply put a spoon full right where the water will enter the bed and it will mix as soon as water flows to the bed.

Fair enough.. each to their own...

I've used the distribution grids with both timed flood & drain... and constant flood... and really haven't had a problem with either....

But it could be a matter of pipe/pump sizing.. and flow rates I guess...