Water submetering means putting a meter on each unit behind the building’s main water meter so each tenant pays for the water they use. In California, SB 7 requires it on most new multi-unit buildings that applied for a water connection after January 1, 2018, and Civil Code 1954.201 to 1954.219 controls exactly how a landlord can bill for it. On an older duplex, fourplex or a lot with ADUs, it’s optional. But it’s one of the few ways to cut a real expense line on an Orange County rental.
Water is the utility small-property owners most often end up paying for without thinking about it. On a lot with a front house and one or two ADUs, there’s usually one meter and one bill, and the owner eats it. Here’s when submetering is required, what it costs, what you can legally charge, and whether it’s worth doing on the property you’re buying.
What Is Water Submetering?
A submeter is a small meter installed on the water line feeding one unit. The water district still bills the owner through the master meter. The owner (or a billing company) reads each submeter and bills each tenant for their share.
- Master meter: the district’s meter at the street. One bill to the owner.
- Separate meter: a second meter from the water district. Each unit gets its own district bill. This often means a new service line and capacity fees.
- Submeter: a private meter behind the master meter. Cheaper and faster than a separate district meter, but the owner handles billing.
- RUBS (ratio utility billing): splitting the bill by a formula like square footage or occupants, with no meter. Common, but less precise than a meter.
When Is Submetering Required in California?
SB 7 (2016) added Water Code section 537.1. It requires each unit to be measured, by a district meter or a submeter, on newly constructed multi-unit residential and mixed-use buildings whose water connection application was submitted after January 1, 2018.
The law exempts a few building types, including qualifying low-income housing, student housing, long-term care facilities, time-shares and senior residential care.
What SB 7 does not do is force you to retrofit an older building. If you buy a 1960s fourplex in Anaheim or a 1950s duplex in Garden Grove, submeters are your choice. The statute also doesn’t specifically mention ADUs, so whether a new backyard ADU triggers it depends on how your water district treats the project. Ask the district at plan check, not after the unit is framed.
What Can a Landlord Charge for Submetered Water?
Once you bill tenants through submeters, the billing rules in Civil Code 1954.205 apply, even on an older building. This table covers the parts investors ask me about most.
| Rule | What the law allows |
|---|---|
| Usage charge | The tenant’s measured share of the water used, at the district’s rates |
| Fixed charges | A share of the property’s fixed water charges, split by usage or equally per unit |
| Billing fee | The lesser of $4.75 per month (CPI-adjustable) or 25% of the usage charge |
| Late fee | Up to $7 on the first late bill and $10 after that, capped at 10% of the unpaid amount in any 12 months |
| Leaks | If a reported leak isn’t fixed within 21 days, usage for that period is limited |
| Water shutoff | Never allowed for nonpayment. Water charges are not rent. |
You also have to give the tenant a written disclosure before they sign the lease. It must include a monthly estimate of the water bill, how and when to pay, and how to report leaks. Tenants can ask for their meter data, and you have seven days to provide it.
The takeaway: submetering is legal and common, but it isn’t a profit center. You recover the actual water cost and a small admin fee. That’s it.
How Much Does Water Submetering Cost?
Prices vary a lot by meter type and how hard the pipes are to reach. Vendor pricing published by SimpleSUB Water gives a useful range:
| Item | Typical cost |
|---|---|
| In-line submeter, new construction | About $150 per unit installed |
| In-line submeter, retrofit | About $250 to $350 per unit installed |
| Clamp-on or wireless meter | About $200 to $1,200 per unit |
| Reading and billing service | About $10 to $22 per unit per month |
On a small property, the monthly billing service is the cost that matters. Many third-party billing companies don’t serve very small properties. On a duplex or a house with two ADUs, most owners read the meters themselves and add the water charge to the monthly rent invoice.
Submetering vs. a Separate Water Meter for an ADU
When clients add an ADU, they often ask whether they should get a separate water meter from the district instead. Under Government Code 66324, a district generally can’t require a new connection or capacity charge for an ADU converted inside an existing structure. A new detached ADU can be required to have one, and the fees can be significant.
| Submeter | Separate district meter | |
|---|---|---|
| Upfront cost | Low (hundreds of dollars) | Higher (service line, meter, possible capacity fee) |
| Who bills the tenant | You | The water district |
| Timeline | Days | Can add weeks to the ADU schedule |
| Resale appeal | Good | Best. Buyers like fully separate utilities. |
Utility hookups are also one of the most common causes of ADU delays. I cover the new deadlines districts have to meet in SB 1196 and ADU utility hookup delays.
Does Submetering Improve Cash Flow? A Simple Example
I keep investment math simple: total monthly payment (PITI) against the rent. Water fits on the expense side of that comparison.
Say you own a front house plus two ADUs on one master meter, and the water and sewer bill runs about $300 a month. That’s $3,600 a year you’re paying for your tenants. With submeters, most of that goes back to the tenants. A $1,000 install pays for itself in three to four months. It also changes behavior. When tenants pay for their own water, usage usually drops.
Where it really matters is the lender’s view. Buyers and appraisers look at what the owner pays. A property where tenants pay their own utilities shows lower expenses, which helps when you sell or refinance. If you’re building toward a multi-unit lot, see how many ADUs you can add to a multi-unit property and how to get two detached ADUs approved.
Orange County Water Districts and Who to Call
Orange County has dozens of retail water providers. Most cities run their own water department, and several areas are served by special districts. The Municipal Water District of Orange County lists the retail agencies. Call yours before you buy and ask:
- Does a new ADU on this lot need its own meter or service line?
- What are the capacity and connection fees for a separate meter?
- Will you allow a privately owned submeter behind the master meter?
- Is there a backflow device requirement for the ADU?
Submeters used for billing also have to meet state measurement standards and can be tested by the county sealer. The California Division of Measurement Standards oversees this statewide.
What to Check When You’re Buying a Multi-Unit or ADU Property
- Who pays water today? Ask for 12 months of water bills, not just a summary on the rent roll.
- Is it a master meter, separate meters or submeters? Walk the property and find them.
- Are current leases written for water billing? If not, you usually can’t start charging existing tenants mid-lease.
- Is the building rent-controlled or covered by AB 1482? Shifting a utility to a tenant can count as a rent change. See AB 1482 and new ADUs.
If you’re comparing a duplex to a house with ADU potential, Are Duplexes a Good Investment? runs both through the same PITI-vs-rent math.
Frequently Asked Questions
Is water submetering required in Orange County?
Only on new multi-unit buildings that applied for water service after January 1, 2018, under SB 7. Older buildings and most existing ADU properties don’t have to submeter.
Can I charge my ADU tenant for water?
Yes, if the lease says so. With a submeter, you must follow the Civil Code 1954.201+ billing rules. Without one, a flat fee or a split stated in the lease is common.
How much can a landlord charge to bill for water?
The admin fee is capped at $4.75 a month (CPI-adjustable) or 25% of the usage charge, whichever is less.
Is a separate water meter better than a submeter for an ADU?
A separate meter is cleaner for resale but costs more and can delay the project. A submeter is the cheaper way to get tenants paying for their own water.
Buy the Lot With the Utilities Figured Out
Utilities are one of the details I check on every property before a client writes an offer: meter location, sewer line and whether a separate meter is even possible. It’s a lot cheaper to know before escrow than after.
👉 Book a buyer ADU consult call to go through your options with Dylan
Prefer to talk now? Call Dylan Serna, ADU Realtor at 714-860-2868.
Dylan Serna | The ADU Realtor | eXp Realty | DRE #02217359
This post is general information, not legal advice. Confirm the rules for any specific property with your water district and an attorney.
