Backyard Aquaponics
A place to discuss aquaponics

I have tried using rectangular section PVC downpipe as nft channel.

The stuff that is about 10 cm x 5 cm in section.

Regards the ends, I have tried using upward pointing elbows... but generally the elbow is not a very tight fit, so loads of mastic is called for - else drip drip drip. In the system below there are no drips but, so many times I have had leaks.

http://www.backyardaquaponics.com/forum ... pic_id=105

I have also tried getting rid of elbows alogether, by making up a wooden jig to guide me regards cutting the sides off at each end of the downpipe by 5 cm and thus form a little 5 cm tongue on the base that is scored with a hacksaw blade, then using a heat gun, folded upward along the score and sealed with bitumen tape against the side ends (again using a heat gun to soften the bitumen).

Worked ... but again not 100 % effective every time. ... but at least this way, you don't have to pay for elbows.

I guess I could try a plastic welder, (They are a lot of fun to use!) However I have not got the correct plastic weld material to hand at present for these downpipes.

Does anyone have an altenative idea of a good, robust, simple and easy fix for this one?

Cheers

Johnnie

Hi Johnnie
Here`s a novel idea, haven`t tested it but it should work
what about inflating a balloon inside the pipe ends? A football bladder might be better if they still make them, or perhaps a section of car inner tube with the valve..vulcanise the open ends and pump it up to seal the pipe.

Another way is to make a male punch and a female die out of wood, (pretty much a square peg in a square hole) heat and press a piece of flat pvc sheet into a square internal end cap.

It might be easier to cut a square of plywood along with a piece of rubber...inner tube again. Place the piece of rubber over the open end of your tube and hammer the plywood square in behind it to create the seal.

Pity they don`t sell end caps for downpipe

Thanks Hex... I thought about using a balloon. I bet the sun over here would stuff them pretty quickly!

Good ideas there, I will certainly have a shot at them!

Stormwater round section pipe ... PVC glue ... leakproof! Close to 100 %.

Rectangular downpipe ... a little more difficult to seal as the tolerances are not anywhere near so tight!

I would love an easy foolproof method!

Keep the ideas coming!

Had another brainwave, i wonder if substituting expanding foam for the plywood might work better?
You`d still need the rubber membrane and maybe a bolt or peg through the pipe so the foam could anchor around it and not slide out.

Necessity is the mother of invention

Johnnie, i might be missing something, but......................

why not heat the pvc down pipe end (i'm not sure if 100C is high enough, but if it is then use a pot of boiling water) Then place he end of it into a vice and CLAMP tight for a minute.You'll find that it will weld to itself.

You can always use a final brush of pipe cement over the seam at the end.

Probably won't look like the best thing in town, but it will seal beautifully.

I think that a heat gun may do it. Boiling water is probably not hot enough. I think that a weld may be needed. (Fiddly).

Thanks for the ideas.

You could dunk it in hot vegetable/sunflower oil, it works pretty good on alkathane pipe (blue water pipe)

Johnnie,
We can get an adapter over here, check and see if they have them down under, that converts the round to the square so that you can use round pvc to go into storage tanks or into an underground pipe. (Prevents run off erosion, or to run into a pond or other catch basin.) Then just glue the adapter on, and either glue on a cap or an adapter for a screw in clean out cap.
Kevin

Wow, people here come up with some complicated solutions.

I would suggest either some PVC sheet, or a rectangular piece cut from left over downpipe. Cut it down to fit perfectly in the end of the down pipe. Then glue with he blue or green pvc cement.

Failing that, or concerned with the pvc glues, cut a piece of 3-4.5mm acrylic and do the same thing except us aquarium silicone in the ends.

Nup, get a roll of material tape( duct tape but stronger) and tape the crap out of it!

if you have a heat gun jonnie your set,

you could use a bit of scrap pvc weld it to the two peices and you should have a good seal

or maybe heat the downpipe and expand it to suit the elbows better

What do you reckon that heat gun glue is made from - any leaching concern?

VB its not a glue gun, just hot air at speed. You use the same piece of kit to shape strawberry towers. Like a hairdryer
Looks like this

Keep in mind that PVC doesn't melt to good. It will soften under heat so you can bend it but, it will never liquify enough to weld together effectively. It begins to burn almost immediately after it melts, so unless you could regulate the temperature, you are going to make a mess of it.

Ooops - thought he said glue gun