I just bought a 26 ft tandem surge brake trailer. The guy redid all the brake lines from front to back and used rubber lines all the way. I keep bleeding the system and I can’t get any pressure. I put a new master cylinder and filled everything with fluid. Any ideas?

I wouldn't do it with rubber lines like that. You can buy a coils of brake line on Amazon that come with fittings.
Are you bleeding it with a pressure bleeder, or trying to use the surge actuator itself? I've never had much luck trying to use the surge actuator itself.
https://www.summitracing.com/parts/mvp-0251

You may have to talk to Motive or get on their website that to find an adapter or rubber wedge setup that will work for your trailer, but this is the only way to bleed brakes, period.
There are others out there on Amazon too.

Last, did he convert the brakes from drum to disc by chance? If so, there is an orifice at the tail end of the MC that needs to be punctured or removed. There are some write ups on this on eTrailer.com and other places, including here on OSO.

I was trying to use the surge activator to bleed them. The brakes are still drum. Thanks for the info!

Out of curiosity Why would you use rubber lines? I just redid all brakes on my trailer. one axle was eoh disc and the second axle was electric drum. I removed all old rubber lines and all brake parts and put all new kodiak equip on my trailer. EOH disc setup on both axles. all new rubber lines with the metal ends on them and new valves. Was just wondering why you said to stay away from the rubber lines. Am I looking for problems by going this route?

I can say that the last two trailers I had were Heritage they ran hard lines close the disc brakes but the last 12" or so was the rubber cased flexible line they are not actually all rubber . I can also say I am with Sydwayz you will have little to no success using the surge brake activator. I have always used the Motive bleeder.

https://www.motiveproducts.com/colle...and-extractors

Too many points for failure, and the rubber expands reducing brake pressure when it's needed most. That's why folks who want performance braking (race cars, lifted trucks, etc.) even go so far as to replace the brake hoses from the hard lines to the calipers with steel braided hoses.

You stated amazon has the stuff I would need. Im not trying to hi jack the op's thread but any chance you could post a link or even pm me it. Maybe I will replace again as I noticed the connectors at the caliper which is the traditional metal stem that comes out of the rubber line has kinked a little and I havent figured out why. But maybe since I just spent all the money to redo all the brakes and bearings I might as well spend a little more to make sure that its done right and wont ever have issues.

The first thing motorcycle racers do is throw away the stock rubber brake lines because we just can’t build enough pressure with them. You can literally feel them expand with your fingertips. And that’s with only 3’ of hose and about 800psi of pressure. Cars run about 2000psi. I can only imagine how mush pressure are on surge brake lines.

Ok just for clarification I know the OP was talking about surge brake setup. I however do not have surge my setup is EOH not sure if that makes any bit of difference. I do know however when I was bleeding the brake system and trying to build pressure when i felt it really got pressure the rubber lines seem to shake and move almost violently for a brief second. I would assume this is caused to the pressure hitting a wall so to speak.

You may have to do a little digging. I know etrailer.com sells stuff too. The most important part is a brake flaring tool. Because I have a race car, I invested in a high end tool, but you can get a cheapy for a single job or perhaps rent/borrow one from a local auto parts store.