No general rule here says to replace an item after a certain number of years or repair it below a certain price. The actual condition, available parts, access and household needs must inform the decision.
Write the two outcomes side by side
For each option, note the affected component, parts or equipment, work needed to reach it and the intended result. Add what remains in place and what remains uncertain. A replacement that leaves the same unresolved drain or supply issue is not automatically a more complete answer.
Ask why the provider recommends the proposed extent of work. If a larger project is suggested because nearby components also appear poor, request the findings for those components. The recommendation should not depend only on a broad description of the home's age.
Include the consequences outside the part
Access, finishes, removal, permits, testing and another trade can change the practical difference between options. A component that is inexpensive may be difficult to reach. A larger replacement may create new connection or space requirements. Put those consequences in the comparison rather than treating them as incidental charges.
Parts support and future serviceability are useful questions too. Ask what is known about compatible parts and who can service the proposed equipment. Distinguish confirmed information from an assumption that something will always be available.
Decide what uncertainty is acceptable
An intermittent problem may not be fully reproduced during a visit. Ask what additional evaluation would change the recommendation and what limitation remains if you proceed now. A provider can offer an option without pretending that every hidden condition has been ruled out.
If the choice is not clear, request a written explanation or another independent assessment. This guide does not select a provider or validate a proposal from a short description. It helps make the decision understandable enough to compare.
Keep the accepted scope and rejected alternatives with their dates. The written-estimate notes cover agreement details, while after-repair records help check whether the work addressed the intended outcome. A good decision leaves a clear reason for what was authorized.