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View Full Version : PVC Pipe Size - What to choose?



Jeff
03-13-2012, 09:40 AM
Ok, I am moving right along with my first aquaponics system! Tank and GB's have been bought. I am almost done with the placement of them in my yard (just awaiting some wood to sit the GBs on).

Now I am planning ahead to my PVC purchases, and I am curious as to your thoughts on what SIZE pipe I should get:

- from pump to GB
- from GB back to tank

Now, let me give a recap of my system. I have THREE 45 gallon grow beds. These are being fed from a 110 gallon tank, and a 500gph pump.

My bell siphons are going to have 3/4" stand pipes.

Given that information, should I use 1" pipes to both deliver water to the grow beds, and 1" pipes to return the water back to the tank?

Or should I stick with a 3/4" size for the entire system?

I would think that obviously the larger the outlet pipes are leading from the GB back to the tank, the quicker the water will drain from the beds. Likewise, the larger the pipe feeding the grow beds, the faster they will fill up.

So with a 3/4" stand pipe for my bell siphon, what would YOU use for the rest of the piping, both for filling the grow beds and draining back to the tank?

keith_r
03-13-2012, 10:10 AM
i'd use 1" for the supply, at least the supply "header", and use reducing tee's to each gb
3/4" standpipe should be ok
are you using a "common" drain"? if so, i'd go at least 3", but individual drains should be ok at 3/4" or 1"

Jeff
03-13-2012, 12:04 PM
With my new setup, there will just be individual drains to the central tank. So imagine a tank, and then above that tank will be three beds: one directly above the tank, and one on either side of it.

My plan was to pump water from the tank to Grow Bed 1 --> Grow Bed 2 --> Grow Bed 3 --> Run Off pipe back to tank (for aeration).

Each grow bed will also drain UNDERNEATH back into the tank.

So if you were to look at the tank, you would see one outbound line (from the pump going to the grow bed), and FOUR incoming lines: one from each bed, and an additional line that's putting back water from the line.

Does that make sense? I am attaching a CRUDE picture. Could you tell me if that makes sense? The only thing I am not sure about is the final line coming back into the fish tank for aeration. Does that look like a good design?

http://diyaquaponics.com/forum/download/file.php?mode=view&id=1682&sid=0d6e424f5a8c2da618ad66db89703837

keith_r
03-13-2012, 04:50 PM
makes sense to me..the only thing i'd do different would be to put the tee for extra aeration before the supply to the growbeds

alex281
03-13-2012, 05:12 PM
I followed the same size for my siphons at a half inch. the bed is about 50 gallons and takes about 5 minutes to drain flooded at 9 inches. stick with one size to keep things simple and be able to have more supplies in case of an emergency reconstruction. you never know when you might have to move things around and having everything the same size will be a big help. also, I doubt a 500 gph pump will lose efficiency if you use a size smaller. (could be wrong as I have no experience with 500gph pumps.) I say go with the 3/4

bsfman
03-14-2012, 06:32 AM
I followed the same size for my siphons at a half inch. the bed is about 50 gallons and takes about 5 minutes to drain flooded at 9 inches. stick with one size to keep things simple and be able to have more supplies in case of an emergency reconstruction. you never know when you might have to move things around and having everything the same size will be a big help. also, I doubt a 500 gph pump will lose efficiency if you use a size smaller. (could be wrong as I have no experience with 500gph pumps.) I say go with the 3/4

I agree with Alex281, except that I think you will find 1/2" is perfectly adequate. I've used 1/2" for my input water with pumps as large as 1200 gpm. I probably had some restriction at that size pump, but for a 500 gpm, it's perfectly adequate - even up to 800 gpm, 1/2" is fine. Plus it's cheaper, lighter, and easier to work with too.

commander
03-14-2012, 06:46 AM
My entire blue barrel system is plumbed from top to bottom with 3/4" pvc. I really didn't do any specific calculations but I did have the thought that I would rather have too much capacity than not enough if I decided to expand the system. I also am very big on using a standard size across a system when ever possible to make maintenance and repair easier.

Jeff
03-14-2012, 09:17 AM
makes sense to me..the only thing i'd do different would be to put the tee for extra aeration before the supply to the growbeds

I was going to do that, but I thought Oliver mentioned to do it the way above. I think it's easier for me to do it the way you describe, but I didn't know if there was a major advantage to running it off the third grow bed. If there is no significant difference, then I would probably prefer to run a T off the pump before the first grow bed to feed back into the tank.

Jeff
03-14-2012, 09:18 AM
you never know when you might have to move things around and having everything the same size will be a big help.

Good point! Thanks for the response, Alex.

Jeff
03-14-2012, 09:21 AM
I agree with Alex281, except that I think you will find 1/2" is perfectly adequate. I've used 1/2" for my input water with pumps as large as 1200 gpm. I probably had some restriction at that size pump, but for a 500 gpm, it's perfectly adequate - even up to 800 gpm, 1/2" is fine. Plus it's cheaper, lighter, and easier to work with too.

It's always been a toss up for me between those two sizes: 3/4" and 1/2". I think the price between the two may be negligible, and I am leaning towards the larger size simply because, as someone else said, it may be more handy whenever I expand the system and move to a larger pump. In that manner, the 3/4 size would be less restricting.

Jeff
03-14-2012, 09:22 AM
My entire blue barrel system is plumbed from top to bottom with 3/4" pvc. I really didn't do any specific calculations but I did have the thought that I would rather have too much capacity than not enough if I decided to expand the system. I also am very big on using a standard size across a system when ever possible to make maintenance and repair easier.

Makes sense to me! Thanks for the answer.

keith_r
03-14-2012, 09:57 AM
you will get higher pressure in your supply lines using 3/4", which could shorten the life of your pump..

Jeff
03-14-2012, 11:37 AM
you will get higher pressure in your supply lines using 3/4", which could shorten the life of your pump..

Wouldn't pressure be higher the smaller I go? So in other words, if I used a 1/2" pipe, the pressure would be higher than if I used the larger 3/4" pipe?

And also, wouldn't that pressure be relieved by having a T-connector to spray water back into the tank for aeration?

keith_r
03-14-2012, 11:58 AM
yes, pressure will go up with smaller pipe.. my first pump had came with 2 fittings, 1/2"x1/2" threadXbarb and 1/2"x3/4" thread by barb.. i used 3/4" tubing for supply lines, but changed to 1" pvc supply when i brought the system into the basement. i have much better flow with 1" pvc.. i did divert some flow back to the ft, but now i divert to a couple of bucket filters, i have valves to regulate the flow to the buckets, no valve on the growbed outlet..so i "set" the flow to the growbeds by increasing or decreasing the flow to the buckets.. i was talking about restricting the output of the pump in regards to it being harder on it..
if you have say 3 outlets from your supply, and none of them are "wide open" you will be restricting the pump

bsfman
03-14-2012, 01:09 PM
i was talking about restricting the output of the pump in regards to it being harder on it..


All pumps have a max head beyond which they can't pump. Any elevation whatsoever begins to restrict pump output. Whether that restriction is gravity induced from head height, or from output line size, or from valves makes no difference to the pump. It doesn't know the source of output restriction. Restricting INPUT to the pump from valves or clogged filters on the input side is bad because the fluid lubrication to the pump impeller is reduced and cavitation can occur when that happens, but restricting the pump output volume is not really going to hurt it.

alex281
03-14-2012, 01:46 PM
also. don't go half inch like I did. I experienced cut off issues at one point and I have to use a t-connector at the bottom of my gb in order for it to cut off. also 3/4 will be better if you plan to expand. also the start with the 3/4 adapter to the end of my half inch stand pipe did not have any start issues with a 150 gph pump. so you should be fine as my system is 50 gallons.

Jeff
03-14-2012, 02:38 PM
yes, pressure will go up with smaller pipe.. my first pump had came with 2 fittings, 1/2"x1/2" threadXbarb and 1/2"x3/4" thread by barb.. i used 3/4" tubing for supply lines, but changed to 1" pvc supply when i brought the system into the basement. i have much better flow with 1" pvc.. i did divert some flow back to the ft, but now i divert to a couple of bucket filters, i have valves to regulate the flow to the buckets, no valve on the growbed outlet..so i "set" the flow to the growbeds by increasing or decreasing the flow to the buckets.. i was talking about restricting the output of the pump in regards to it being harder on it..
if you have say 3 outlets from your supply, and none of them are "wide open" you will be restricting the pump

I do plan to have 3 outlets with bell valves on each grow bed, in addition to a valve off the pump to aerate the tank a little bit. My plan would be to use this aeration line to take any remaining pressure off the pump which may be restricted by partially open grow bed valves, if that makes any sense.

In other words, I will start with the grow bed valves all the way OPEN, no restriction. I will then close them a little until I reach the desired flow output that I want. Let's say that I end up closing the valves by 50%. I would then open up the valve near the pump by at least 50% in order to take that pressure and return it back into the tank.

At least that's the plan in theory. :?

Jeff
03-14-2012, 07:48 PM
I just came back from buying a lot of my PVC supplies. I think the only thing I'm really missing now is my 2" bell cover and the 3" media guard.

I do have a question on glue though, and perhaps I should make this a separate topic. What PVC glue should I use? After all, I assume it has to be fish and plant safe. I bought something called "All Purpose Adhesive Sealant --- Aquarium Safe", but that is more for the seal around the opening of the grow bed holes I will cut (I think).

Here is a picture of it:

http://diyaquaponics.com/forum/download/file.php?mode=view&id=1685&sid=d6408cc0eeba5f3e36ab53d8f1bfae02

So is there a specific brand or source for what I should use to glue the rest of the PVC together? Would this stuff work for the entire system?

commander
03-14-2012, 08:02 PM
If you are going to glue up the joints permanently, you should use PC cement and PVC primer. I always just slip fit my joints until I get it just like I want it. It will leak a little but not to much.

Bioritize
03-15-2012, 02:13 PM
Hey Bro,

I would use a 6" drain guard so you can get your hand down there and work if you want to modify something. I will be using this on all my future projects, the 3" is to damn small to get your hand in.

Also, if you can get an air pump and some air diffusers and put them in the fish tanks and if you can in the bottom of each grow bed. I always end up wanting to add this after I put in rocks. The place I am usually lacking is in dissolved Oxygen which is the name of the game.

Good luck

Jeff
03-15-2012, 04:11 PM
Thanks for the advice! I just purchased my 2" PVC for the bell part of my siphon. I still have no idea how I am going to cut notches out of the bottom like I see a lot of people do. Do you think I could just drill a few holes in the bottom to compensate for that, which will allow the water in there?

As for the drain guard, I like that idea. I will probably do that, since I cannot find 3" PVC anywhere.

alex281
03-15-2012, 05:01 PM
heres 2 ways to make the holes. get a fat drill bit and drill a bunch of holes as low as possible. or you could get a little hack saw and cut as if you were going to cut out a v. this will create a bunch of triangle holes that work fine.

definitely get the bigger size guard. i couldnt get my hand in there to save my life with my 3" guard.