Not sure what your pressure is but this looks like 1" PVC. That, and conventional Blu-glue should easily withstand domestic mains pressure.
It is unlikely to be the 90° bend causing the problem. It is likely to be the quality of the join.
- Dig a decent sump under the bend, extending at least 2 ft either side.
- Drain the line.
- Pump the sump dry.
- Cut the offending elbow out.
Inevitably some water will be lost into the sump.
- Pump the sump dry again.
- Cut each arm of the line back 6" to 12"
- Thoroughly clean and dress both ends. There should be no rough ends and no swarf remaining. Fine emery paper is good. DO NOT reduce the OD of the pipe. Ok to roughen though.
- Obtain and dry fit replacement pipe.
You will need 2 x female-female straight joins, a replacement elbow and two appropriate lengths of pipe, a pot of blu-glue and a pot of primer (usually red in colour).
Beware the primer is usually methyl-ethyl-ketone based. Do not breathe the fumes or get it on your skin. Use appropriate chemically resistant gloves, it will eat straight through many plastic gloves.
- Ensure all surfaces are clean and dry. Not moist, not damp, DRY. Ideally use lint free cloth.
- Pre-assemble the elbow, lengths of pipe and joiners.
Prime each surface to be joined. Apply a liberal coat of glue to each surface.
Do not apply glue to the inside ends of the joins that will mate to the existing pipe at this stage.
Don't go crazy, the glue is very forgiving but all surfaces should be wet. More is not better.
Do not take too long, the glue dries quickly.
Push fit the parts together. Leave to dry. An hour is plenty in warm weather.
- Put a piece of plastic or tarp under the ends of the existing pipe. remember we want clean and dry.
- Prime the ends of the existing pipe.
- Apply glue to the ends of the existing pipe and the inside of the joiners.
- Push fit.
- Leave at least a couple of hours.
Slowly turn the water back on. Check for leaks. I will be VERY surprised if you get any.
I hope this is not too tedious but as you said you have no experience I wanted to give you a clear step by step.