Backyard Aquaponics
A place to discuss aquaponics

I want to design this system so that I dont run into many problems with clogs. What diameter pvc pipe should I use? I tend to massively overengineer my projects.... Any drawbacks beside posible fast draining? Is that even a drawback? Please only vote if you have designed a system and speak from experience.

I have used 40mm (1-1/2") as the drain pipes on all my GBs and never had any clogging or "too fast" draining problems - here is a test I was doing using a bell siphon to drain a 2m x 1m GB

Water was pumped up to the GB via the black hose - disregard all the superfluous pipes and junk hanging off the GB (this was a (successful) test )

if you want to use only one size for supply and drain then go the 40mm

otherwise use 40mm for drain and 25mm for supply.

PS i think your conversions are out

I use 20mm pipes from the pump as that is the outlet size - I only use small continuous pumps

...larger sizes than 40mm for the drain pipe could be used but only use smaller sizes if the AP system is also small

+1 for 40mm and 40mm

I use 25mm for irrigation lines that are under pressure, and 40mm for drains.

+1

I use a lot of 40mm, in fact almost all of it is 40mm... I started with 13mm and only ran into problems - especially as my valves would easily block up with fish poop etc... Since going to larger diameters I have had less blockages and saved a lot more water ... My aim is to rid my system of the last bits of 13mm and have nothing smaller than 19mm.
Just about all my drains will be 40mm by the end of this week and sometimes they drain into a main 100mm pipe which feeds back to the main (sump) tank.

aquamad - the 13mm route is frought with peril Coming home nearly everyday to an empty fish tank....

I voted for the 1.5 inch pipe.

Here are my pipe size experiences.

First, use the pipe size that your pump wants or larger, never restrict your pump!

In my tiny systems, I have used the 1/2 inch black irrigation pipe that fits the pump outlet. I have found that these do start to get gunked up eventually and sometimes need some maintinance. That is for the feed from the pump to grow beds or up to fish tank in CHIFT PIST systems. Drain lines should always be larger than the inflow. My tiny systems have 3/4" drains and overflows.

The Bigger system has 1.5 inch pipe to and from the pump. I Tee that down to 1 inch ball valves at each of the standard grow beds.
I do have one little half barrel grow bed that I split off to 1/2 inch pipe and ball valve, it gets gunked up all the time and the plants in that bed will probably be dead when I get back to town, bad idea that.
My drain holes in the big system are mostly 1.5 inch, they mostly drop into 3" or 4" pipes to flow back into the main system or over to the monster bed. Sump pump in the monster bed gets 1.5 inch pipe back to the main tanks. I do have 1" loop siphons in that system as well as 1.5" bell siphon and a 1.25" flout. All the drains seem to work fine since they drop into an open pipe where the siphon can break and the large pipe drains back to system.

Probably best sizing your pump for your future planned system plus some. Get pipe that is the right size for your pump system.

It might be nice to get all one size but do remember that fittings get more costly as size increases. As do ball valves. Reducing Tees to stub out to grow beds will save you the difference between the sizes of ball valves. In household plumbing, the sizing usually reduces as you split off for more fixtures, this can help keep pressure at the different fixtures more even. It made sense to me to reduce the pipe size as I stubbed out for the grow beds. Just don't go too small as then you get clogged.

Oh, I forgot to mention that if doing a CHIFT PIST system, the piping feeding the grow beds should be large as they are for gravity drain. Water being pushed by a pump is under more pressure and therefore doesn't require as large a pipe to provide the same flow.