24v pump questions

I just signed up here and need to learn a bunch about solar power. I was a power plant millwright/nuke pipe welder. My off-grid garden irrigation system is having problems and I need to troubleshoot it and I need some advice on a new pump.

I currently have an RPS 400-watt system with the 24v solar pump at 85 feet. Well static level is 38 feet. I’m charging 2 each 12v AGM batteries wired in series to give me 24vdc for my Shurflo 2088 series delivery pump. The supply line to the pump is a ¾” PVC line coming off the bottom of a 1600-gallon storage tank. The tank is sitting on the ground and the delivery pump is located about 3 feet off the ground and about 3 feet away from the tank. I also have a pressure tank in the discharge line.

At the start of last year’s garden, the delivery pump supplied water and ran the Rainbird sprinkler with no problem. Near the end of the season, it would not maintain enough pressure to run the sprinkler. I opened the pump/diaphragm and there’s no trash in it but it still won’t maintain pressure like it did. My batteries are holding a full charge, so it’s not low voltage.

The long-term plan for this irrigation system is to supply water to our house during a power outage. We’re 15 miles inland from the Gulf coast in central Florida. Sooner or later, we’re going to have a hurricane or something that kills the power here. So far, we’ve been lucky, but I want to be prepared for it. My storage tank is about 100 yards away and maybe 8 feet lower than our house. I have a ¾” PSI coil pipe with an isolation valve near the house that ties into the house system. The plan is to open that valve and still have running water during outages if need be – gotta keep Mama happy.

Now for the actual questions – do the Surflo 2088 pumps require rebuilding every few months of regular use? Is there a more durable pump available at a reasonable price? I see there is a scb 20-25P-2 multistage pump available for around $900. I can add more batteries since that pump requires between 700 & 800 watts but will my existing 400-watt solar panels support the extra batteries?

I can rebuild my Surflo pump for about $40 but I’d hate to have it puke again when we really depended on it. What are your thoughts?

Thanks for any input!