Plastic intake pipes do provide for suction leaks. You might do yourself a favor and take a step back, and look at the overall picture. If you want to hose water from the shallow well, you need to turn it into a complete water supply, with a pressure switch and a storage tank and a relief valve. Then you can use a hose and no worries. The sprinkler system backflow protection now gets upgraded to a pressure vacuum breaker, on account of it is now under pressure 24/7
If this seems like a lot of time and expense for a little bit of extra watering, it is just that. You'd be better off improving the sprinkler zones themselves, and buying an extra-long garden hose for whatever remains unwatered by the sprinklers..