In part 2 of the Albin Ballad 30 refit we rebuild the v-berth by moving the chain locker bulkhead aft and replacing the original plastic 18 gal water tank with a 45 gal integral tank constructed out of divinycell foam board and fiberglass instead of plywood. This saves a little weight but ensures no future rot if there is a pinhole leak in the fiberglass somewhere. Here is an article detailing integral water tank construction: https://atomvoyages.com/integral-wate...

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The access plate is from Defender.com, Beckson DP60-W: https://www.defender.com/product3.jsp...
The plumbing fittings I get from West Marine because I get wholesale prices so you might shop around for best price. Below are West Marine model numbers:
2 pieces tank site tube 90° Plastic Mushroom Head Barbed Thru-Hull, model # 336230.
1 piece 1/2" thru-hull outlet, Model # 411340.
2 pieces 5/8" thru-hull for vent and chain locker drain, Model # 401929
1 piece clear PVC tubing for site tube. Model #103499
Optional - You might reuse your existing deck water fill fitting. But I now prefer not to install the deck inlet to save cost and clutter and because the tank should be filled by pouring the water jugs into the tank access plate or bringing the hose thru the forward hatch and into the access plate so as not to overfill and stress the plastic access plate seal. If you do use a deck fill, then best to pump out about a gallon of water at the sink spout to address that issue.