ADU Questions · 2026
How Do ADU Utility Hookups Work?
ADU utility hookups, water, sewer or septic, electrical, and sometimes gas, are coordinated as part of Framework First’s all-inclusive build. Depending on what your existing service can handle, your ADU either connects into your primary home’s existing water, sewer, and electrical lines, or it gets a new dedicated connection of its own. Which route your property needs is identified during the feasibility study and site visit, not guessed at after the home shows up.
The short version: Utility hookups are included in the all-inclusive price, not billed separately after the fact. Whether your ADU shares your home’s existing service or needs new dedicated lines depends on your specific property’s capacity, and that gets confirmed during the feasibility study and site visit, before you sign a contract.
What “utility hookups” actually covers
When people ask about hookups, they usually mean four things:
- Water, either a shared line off the main house’s service or a new connection
- Sewer, tying into the existing sewer lateral, or septic if the property isn’t on a public sewer system
- Electrical, either sharing capacity from the home’s panel or adding new dedicated service
- Gas, if the ADU’s appliances call for it (many ADUs go all-electric instead)
All four are part of Framework First’s project pricing, not a separate line item you negotiate later. A permitting budget, the foundation, the factory build, delivery, and final inspection are built into that same price from day one, with your exact permit costs confirmed for your property in the feasibility study.
Shared connection vs. a new dedicated connection
This is the part that actually varies property to property, and it’s the reason nobody can give you a blanket answer over the phone.
Some homes have enough spare capacity, water pressure, sewer lateral size, electrical panel amperage, that the ADU can simply tie into what’s already there. Others don’t, either because the existing service is older or smaller, or because adding a second full dwelling pushes past what the current connection was sized for. In that case, the ADU needs its own dedicated line run from the street or a new meter.
Neither option is inherently better or worse. It comes down to what your specific lot, house, and existing infrastructure can support, and that’s an engineering and code question, not a preference.
| Utility | Shared connection | New dedicated connection |
|---|---|---|
| Water | Tied into existing home service, if pressure and capacity allow | New meter or service line, if the existing one can’t support a second dwelling |
| Sewer | Tied into existing sewer lateral, if sized correctly | New lateral, or a septic system where public sewer isn’t available |
| Electrical | Sub-panel off the existing panel, if there’s spare capacity | New dedicated panel or service upgrade |
| Gas | Tied into existing gas line, if used | New line, or the ADU is built all-electric instead |
Water, sewer, and septic
Most properties in Framework First’s service area are on public water and sewer, and for those, the question is really just capacity: can the existing lateral and meter handle a second dwelling, or does the ADU need its own.
Some properties, particularly in unincorporated parts of Monterey, Santa Cruz, and San Benito counties, are on well water or a septic system instead of public service. That’s not a dealbreaker, but it does change the process. A septic system has to be sized (and sometimes inspected or upgraded) to handle the added load of a second unit, and your local environmental health department is typically involved in sign-off alongside the building department. If your property is on septic or a well, this gets flagged and scoped specifically during your feasibility study rather than assumed one way or the other.
Electrical and gas
Electrical works the same way. Many ADUs run comfortably off a sub-panel connected to the main home’s existing electrical service, especially since a lot of Framework First models use efficient mini-split heat pump systems rather than higher-draw equipment. Others need a panel upgrade or a new dedicated service, usually because the existing panel is older, smaller, or already near capacity from the main house.
Gas is the most property-specific of the four. Some ADUs are built all-electric and don’t need a gas connection at all. Where gas is used (typically for a range or water heater), it’s either tied into the existing line or run new, depending on distance and existing capacity.
How Framework First figures out which route your property needs
This is exactly what the feasibility study and the in-person site visit are for. Our team looks at your existing water meter and service line, your sewer lateral or septic system, your electrical panel’s age and available capacity, and whether gas is used or needed, and identifies which utilities can be shared and which need a new connection. That assessment happens before your final contract, so the utility approach, and its cost, is baked into your all-inclusive price rather than surfacing as a surprise mid-build.
You can see how this step fits into the overall build sequence on our process page, and compare all-inclusive pricing across our model lineup on the pricing page. If you’re not sure which floor plan fits your lot and utility situation, our models page is a good place to start.
Frequently asked questions
Does my ADU need its own water meter?
Not always. If your existing water service has enough capacity and pressure to support a second dwelling, your ADU can share it through a new line off the main service. If it doesn’t, a new dedicated meter or connection is added. This is confirmed during your feasibility study, not assumed either way.
What happens if my property is on septic instead of public sewer?
The septic system has to be evaluated for whether it can handle the added load of a second unit, and your local environmental health department is typically part of that sign-off alongside the building department. This is common in unincorporated parts of Monterey, Santa Cruz, and San Benito counties, and it’s identified and scoped during your feasibility study, well before construction starts.
Are utility hookups included in the all-inclusive price, or billed separately?
They’re included. Water, sewer or septic, electrical, and gas hookups (where used) are part of the same project price as the foundation, the factory build, delivery, and final inspection, alongside a permitting budget. Exact permit costs are set by your city and confirmed in your feasibility study before you sign, and property-specific site work like a septic upgrade is priced there too rather than assumed into the model price.
When do utility hookups actually happen during construction?
Hookups happen on-site, around delivery day. The foundation and any necessary utility connections are prepared on your property while your ADU is being built in the factory, and the final tie-ins, water, sewer or septic, electrical, and gas, are completed after the home is crane-set on the foundation, ahead of final inspection.
Will I know in advance if I need a costly utility upgrade?
Yes. That’s the purpose of the feasibility study and site visit, to identify capacity issues, like an undersized sewer lateral or an aging electrical panel, before your contract is finalized, so there are no surprises once construction is underway.
Ready to find out exactly what your property’s water, sewer, and electrical service can support? Start your feasibility study and get a straight answer before you commit to a model.