Leak down test

+1 on that POR sealant. I've used it twice and the results are excellent.  

There is a similar product called Red Kote 

I have used KBS sealer kit in this tank which seems to be failing. I bout the 3 stage kit n galloped it to the letter n now have going on. Pics show some flaking but some small rust spots n places where the sealant is gone showing bare steel. 
So the tank was bone dry today so I poured 1ltr of Ranex rust converter, coated every part of the tank. So the Ranex has now been drained n tank is drying. Heading off for a few days on Sunday so it will be bone dry when we get back. I will be fitting an extension onto the fuel outlet pipe to raise the fuel pick up height n leave any remains crap on the bottom.

If you want to come out of the bottom of the tank one of these will solve all your problems. All aircraft have them. You could make one up with even finer mesh in 15 minutes. They stop anything that will block a line leaving the fine powder stuff only to be picked up by the normal filter while being almost impossible to completely block themselves.

You can adapt this system to be attached to a top draw pick-up pipe ie make up a pencil size tube of fine mesh about 50mm long and either solder or epoxy it to the end of the pick-up pipe. Even a small jubilee clip would do the job to hold the mesh tube onto the pick-up pipe.

 

In  the past I have made something similar and in  fact one is in the small tank. I will take a pic of it tomorrow. I use a stainles product called Termimesh which is used for termite protection in houses.

If you can find some of the old metal mesh off a fly-wire door that is the perfect solution. Nearly all plastic now.

Termimesh is great stuff, fine hole spacing and able to be formed into shape with a bit of work
Gumpy

My Termimesh filter. It's stainless steel with fine holes. I rolled it up like a ciggy n poked it down the bore of the tube then crimped the end shut.

So git to play with David for a short time today. I made the extension tube n soldered it in place. Fitted the fuel tank n dash then dropped the bonnet in place as one bolt goes through the bonnet n onto the tank. Fitted the fuel line with the extension then poured some fuel into the tank. I put a hose from the fuel line from the tap into a buck n turned on the tap. Nothing. Thought maybe not enough fuel in the tank. But I blew into the plastic tube n heard bubbles then fuel flowed freely into the bucket. But I noticed the tap handle leaked. So once the tank was empty I removed the tap handle. I knew the thread was the issue, it's worn n the nut wobbles on the thread. So with another one of my nasty thoughts I cleaned the thread n sweated solder over the worn thread then ran the 1/4" BSF die down it. Brilliant success. The nut nut no longer wobbles n good tension on the spring to pulle the handle onto the gasket. Then I noticed another leak between tap housing n glass bowl housing. This is usually a fibre washer so this is for the next play day. 
I put fuel back into the tank n turned it on n once again no flow but blow into the plastic tube, hear bubbles then it flows WHY?

I have learnt after many decades of owning irrigation pumps that the key to stopping the suction side blocking is to slow the flow down to almost zero as it enters the strainer

Yes pointless waffle here

So some things I have learnt

If you double the diameter you get 4 times the flow
Some things like mesh filters actually increase the flow and increase the chanes of a blockage

Using a screen is a good idea but the screen needs to be a lot bigger to maintain the same flow

Remember as the flow rate increases the velocity increases and the chances of a blockage climbs on a really steep graph

So to reduce the chance of a blockage the flow rate has to fall
To reduce the flow rate you need to increase the surface area

I'm sure your all over this Cobba

Paul

Paul

That is exactly what those finger strainers do. 

Say the pipe is 5mm id the sum of all the holes in the strainer might be 20 or 30 times more than that so the flow through each hole is only required to be 5%  that of the flow going into the neck of the pipe. Achieving your aim of not jamming rubbish against the inlet by forceful flow. If Cobba made his strainer 150mm long the flow into each mesh hole would be hardly measurable.