Retirement Plans for Plumbing and HVAC Business Owners: Solo 401(k), Safe Harbor, and Union Considerations
Plumbing and HVAC business owners earning $100,000-$250,000+ in net profit can shelter $40,000-$70,000 per year in retirement plans. The plan choice depends on the business structure: a solo operator or owner-and-spouse team uses the Solo 401(k); a company with journeymen, apprentices, and office staff needs a plan that includes those employees. Union plumbing and HVAC companies have an additional layer: union members typically participate in a multi-employer pension plan through the union, and the employer’s contribution to that plan is a separate, mandatory expense.
A solo plumber or HVAC technician (no employees other than a spouse) should use the Solo 401(k): $23,500 employee deferral (2025) plus 25% of net self-employment income (or W-2 salary for S-Corp owners) as an employer contribution, up to $70,000 combined. A company with non-union employees uses a Safe Harbor 401(k) with a 1-year, 1,000-hour eligibility requirement: this allows the owner to defer $23,500 plus employer contributions while limiting the cost of covering employees (apprentices who leave within a year never become eligible). Union companies contribute to the union pension fund on behalf of union members (typically $5-$15 per hour worked, negotiated in the collective bargaining agreement) and may offer a separate retirement plan for non-union employees (office staff, non-union technicians). The union pension contribution is deductible as a labor cost, not a retirement plan contribution, and does not limit the owner’s ability to contribute to their own plan.
How does the Solo 401(k) work for a solo plumber?
What about companies with apprentices?
Plumbing and HVAC companies that train apprentices face a common retirement plan challenge: apprentices often cycle through the business during their 4-5 year training period, and turnover is significant in the first year. The 1-year, 1,000-hour eligibility requirement for a Safe Harbor 401(k) excludes apprentices who leave within their first year.
For apprentices who stay and become eligible, the Safe Harbor 401(k) requires a 3% non-elective contribution on their compensation. An apprentice earning $35,000/year receives a $1,050 employer contribution. For a company with 4 eligible apprentices, the annual cost is $4,200, which is modest compared to the owner’s $23,500+ in personal contributions.
What about union pension obligations?
Union plumbing and HVAC companies contribute to multi-employer pension plans (such as the UA National Pension Plan for United Association plumbers and pipefitters). The contribution rate is set in the collective bargaining agreement, typically $5-$15 per hour worked by union members.
These contributions are deductible as a cost of labor (they are part of the negotiated compensation package). They are not “retirement plan contributions” in the sense of the employer’s own plan. The owner can still maintain a separate retirement plan (Solo 401(k) if no other employees, or Safe Harbor 401(k) for non-union staff) without any conflict with the union pension obligation.
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- Plumbing Hvac Insurance Bonding
- Plumbing Hvac Worker Classification Apprentices
The Business Assessment is a fixed $250. You get a written, CPA-reviewed retirement plan comparison that accounts for your employee structure, union obligations (if any), and the S-Corp salary interaction.
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Yarik Yarosh, CPA. "Retirement Plans for Plumbing and HVAC Business Owners: Solo 401(k), Safe Harbor, and Union Considerations." Blue Cloud CPA, September 5, 2026. https://bluecloudcpa.com/guides/plumbing-hvac-retirement-plans
This guide is general information, not tax advice for your specific situation. Which points apply, and how, depends on your facts.