Cost to Fill a Pool
From your gallons and your water rate — with the sewer-exemption money-saver and the per-1000-gallon vs per-CCF unit clarity most calculators don't bother with.
Hook
The charge you might not owe.
Filling a pool costs less than most people fear — usually around a hundred dollars for an average pool on city water — but it can cost more than double that for a reason almost nobody catches: your water bill probably charges you for sewer service on every gallon, and pool fill water never goes down the sewer.
Many utilities will waive that charge if you ask. The difference on an average pool is over a hundred dollars, every fill.
Promise
This calculator works out what filling your pool actually costs — from your pool's volume and your water rate, in whichever unit your bill uses (per thousand gallons or per CCF, which trip people up). It shows the water-only cost versus the water-plus-sewer cost so you know what to ask your utility about, and it compares municipal water to trucked delivery for the cases where that's a real question. Honest about being an estimate built on your rate.
Here's the deal: fill cost is just your pool's gallons times what your water costs per gallon — the trick is in the “what your water costs” part. Bills price water in different units, and most bundle a sewer charge you may not owe on fill water. Get those two things right and the number is simple; miss them and you either overpay or misread your bill by a factor of seven.
What you'll give us
Your pool's volume (jump to the volume calculator if you don't know it), your water rate in whichever unit your bill uses, and a sewer choice — water-only or water+sewer. We always show both, so you know what to ask your utility about.
The calculator
Fill the fields, hit Calculate. The result panel shows BOTH the water-only and water+sewer costs as ranges, the potential sewer-exemption savings, and (optionally) a trucked-water comparison.
The sewer charge you might not owe
Here's the part worth reading before you fill. Your water utility almost certainly charges you two ways for water: the water itself, and a sewer fee based on how much water you use — the logic being that water in usually means water out, down the drain.
But pool fill water doesn't go down the drain; it sits in your pool. So you may be paying a sewer fee on thousands of gallons that never touch the sewer. Many utilities know this and will credit it — sometimes automatically, sometimes only if you call ahead, sometimes through a separate “fill meter.”
On an average pool that's well over a hundred dollars. One phone call before you fill can halve the bill.
Utility policies vary — some waive automatically, some require a form, some require you to fill from a separate meter. The calculator shows you both numbers so you know what to ask about; the savings figure is the spread, never a promise.
Reading your water rate right
Before the calculator can help, you need your water rate — and that's where bills get confusing, because they don't all use the same unit. Some charge per thousand gallons; others charge per “CCF,” which is a hundred cubic feet, or about 748 gallons.
Those are wildly different units: a rate that looks like five dollars could be five per thousand gallons or five per 748 — and confusing them throws your estimate off by a factor of seven and a half. Find the unit on your bill, pick it here, and enter the matching number.
City water vs trucked delivery
Most people fill from the tap, and for a routine fill that's almost always cheapest — around a hundred dollars on city water. Trucked water gets asked about when there's no municipal supply, a drought restriction on outdoor use, or a remote property.
It's convenient and fast, but it's not cheap: at roughly a dime a gallon delivered, filling an average pool runs into the low thousands — perhaps twenty times the municipal cost. Worth it when the tap isn't an option; rarely worth it when it is.
Filling is one-time; running costs aren't
One thing to keep in perspective: filling your pool is mostly a one-time cost — the initial fill, or refilling after a drain. It's not a recurring bill like running your pump or heating the water. Topping up for evaporation is real but small (our evaporation calculator covers that).
And the fill cost is just the water — a fresh fill still needs its startup chemistry balanced, which is a separate job and a separate cost. Start at the volume calculator and run through the chemistry cluster from there. Budget the fill once, then think about the ongoing costs separately.
Where the numbers come from
Five short steps from gallons + rate to a dollar figure. EXACT math throughout — the only thing in the model that's an estimate is your editable rate.
Step 1 · gallons from the volume calculator
Volume in your unit converts to gallons via the shipped
volumeToGalfunction — the same NIST-exact conversion the volume calculator uses. Cross-cluster reuse: chemistry's engine handles the unit math here too, so the fill calc and the volume calc cannot disagree on how many gallons your pool holds.Step 2 · pick the billing unit, then read your rate
US water utilities bill per 1,000 gallons OR per CCF (a hundred cubic feet =
748.052gallons). EXACT unit conversion. Read the unit on your bill before entering the rate — confusing per-1000-gal with per-CCF is a ~7.5× error.Step 3 · cost = volume × rate (the engine)
For the standard 20,000-gallon pool at $5 per 1,000 gal:
20000 / 1000 × $5 = $100.00. Per CCF at $4:20000 / 748.052 × $4 ≈ $106.94(= 26.74 CCF). EXACT physics; the only approximation is the rate.Step 4 · the wedge — BOTH water-only AND water+sewer
Same model, two rates. Water-only at $5/1000 = $100. Water+sewer at $12/1000 = $240. Gap = $140 EXACT on the standard system — the sewer-exemption opportunity. The engine returns both costs by construction; the page cannot hide one side of the comparison.
Step 5 · doubly an estimate (the honesty boundary)
Cost = your volume × your rate. Both are user-editable. The math is exact; the rate varies enormously by region (~$2–$6 per 1,000 gal is common but ranges widely) and your utility's sewer policy varies by city. We surface a range, never a false-precise single number, and we say “ask” about the exemption rather than promise you a saving.
Eight worked examples
Engine values, never hand-typed. Costs are estimates at the labeled rate; the gallon math is exact.
E1 — How much does it cost to fill a pool? (the core case)
20,000-gallon pool at $5 per 1,000 gallons water-only: $100.
Takeaway: An average pool runs about a hundred dollars to fill on city water — less than most people expect.
E2 — Per-CCF billing (read the unit right)
20,000 gallons at $4/CCF (1 CCF = 748.052 gal): $106.94 (= 26.74 CCF × $4).
Takeaway:If your bill uses CCF, that's 748 gallons per unit — pick the right unit here or your estimate is off by 7.5×.
E3 — The sewer trap (the wedge — the money-saver)
20,000 gallons billed water+sewer at ~$12/1000: $240 vs water-only ~$100. Gap: $140 EXACT.
Takeaway:If your utility charges sewer on the fill, you're paying double — call and ask for the pool-fill exemption; fill water never enters the sewer.
E4 — Is trucked water cheaper than city water?
20,000 gallons trucked at $0.10/gallon: $2000 vs $100 municipal — about a 20× ratio.
Takeaway:Trucked water costs roughly twenty times the tap — worth it only when the tap isn't an option.
E5 — Cost by pool size (linear)
| Gallons | Cost at $5/1000 water-only |
|---|---|
| 10,000 | $50 |
| 15,000 | $75 |
| 20,000 | $100 |
| 30,000 | $150 |
Takeaway: Fill cost scales straight with volume — double the gallons, double the cost.
E6 — Exemption savings by size
| Gallons | Sewer gap (savings if exempt) |
|---|---|
| 10,000 | $70 |
| 20,000 | $140 |
| 30,000 | $210 |
Takeaway: The bigger your pool, the more the sewer exemption saves — always worth the call.
E7 — Top-off vs fill (the framing)
A full fill is ~$100; a month's evaporation top-off is roughly an inch or two — a few hundred gallons, a few dollars.
Takeaway:The big cost is the one-time fill; evaporation top-off is minor — don't conflate them.
E8 — Metric (75 m³ via the shipped volume engine)
75 m³ → 19812.9 gallons via the same NIST-exact L_PER_GAL the volume calculator uses. At €1.50/m³: €112.50.
Takeaway: The math is identical in metric — volume × your rate — and the fill calc reconciles with the volume calc on the same shared conversion.
Reference tables
T1 · Fill cost by pool volume × water rate
ESTIMATE · cost = gallons × rate, EXACT math but rate is regional. Dollar figures shown for the 3/5/8/12 per-1,000-gallon rate band (your bill knows).
| Gallons \ rate $/1000 | $3 | $5 | $8 | $12 |
|---|---|---|---|---|
| 5,000 | $15 | $25 | $40 | $60 |
| 10,000 | $30 | $50 | $80 | $120 |
| 15,000 | $45 | $75 | $120 | $180 |
| 20,000 | $60 | $100 | $160 | $240 |
| 25,000 | $75 | $125 | $200 | $300 |
| 30,000 | $90 | $150 | $240 | $360 |
T2 · Sewer-exemption savings by pool volume (the wedge dataset)
EXACT physics (linear in volume) · the gap between water-only ($5/1000) and water+sewer ($12/1000) typical rates. The amount your utility may waive if you ask.
| Gallons | water-only ($) | water+sewer ($) | savings if exempt ($) |
|---|---|---|---|
| 10,000 | $50 | $120 | $70 |
| 15,000 | $75 | $180 | $105 |
| 20,000 | $100 | $240 | $140 |
| 25,000 | $125 | $300 | $175 |
| 30,000 | $150 | $360 | $210 |
T3 · Municipal vs trucked water by volume
ESTIMATE · municipal at $5/1000 (typical), trucked at $0.10/gallon (typical delivered). Real only when the tap isn't an option.
| Gallons | municipal ($) | trucked ($) | ratio |
|---|---|---|---|
| 10,000 | $50 | $1000 | 20× |
| 15,000 | $75 | $1500 | 20× |
| 20,000 | $100 | $2000 | 20× |
| 25,000 | $125 | $2500 | 20× |
| 30,000 | $150 | $3000 | 20× |
Tables released CC BY 4.0. T1 + T3 are estimates at typical rates; T2 is exact in the gap calculation but rates vary.
Methodology & sources
Cost = volume × water rate. EXACT math. Volume comes from the shipped volume calculator's engine — the same volumeToGal function, the same NIST-exact L_PER_GAL constant. Cross-cluster reuse: the 4th cluster reaches into the 1st the same way the hydraulics anchor reached into chemistry. The fill calc and the volume calc cannot disagree on how many gallons your pool holds.
Both billing units handled. Per 1,000 gallons is direct. Per CCF (= 100 ft³ = 748.052 gallons) is via that one EXACT unit conversion. Reading the wrong unit overstates or understates by ~7.5× — we surface the unit choice explicitly so the trap can't close.
The sewer-exemption wedge.Many US water utilities bill water and sewer together, charging a sewer rate on every gallon used — the assumption being that water in implies water out. Pool fill water doesn't enter the sewer; many utilities will credit the sewer share if you ask, sometimes through a separate fill meter, sometimes through a one-time exemption, sometimes automatically. We can't know your utility's policy, so we show BOTH costs — water-only and water+sewer — and surface the gap as your potential savings. Shown, never promised.
Doubly an estimate. Your volume varies; your rate varies; both are user-editable. We show a range, never a false-precise single number. US water-only rates commonly fall $2–$6 per 1,000 gallons; the typical defaults are labeled as such.
Trucked-water comparison is present (~$0.10/gallon typical delivered) but never pushed — for a routine fill the tap is roughly 20× cheaper. It's a real option for no-supply, drought, or remote properties.
Scope.This page is the fill cost only — the one-time water cost. Startup chemistry (a fresh fill needs it) is the chemistry cluster's job; ongoing evaporation top-off is the evaporation calculator's job. Honest cross-links, not scope creep.
The 4th cluster anchor.This page opens a new “Pool Water & Filling” cluster — the same way volume anchored chemistry. The hub page ships when the cluster has at least two spokes (the fill-time calculator joins next). Until then the cluster is in the master index but the hub link is suppressed everywhere via a per-cluster hubLive flag.
Reference tables T1/T2/T3 released under CC BY 4.0. Math exact; dollar columns estimates at the editable rate.
Frequently asked questions
- How much does it cost to fill a pool?
For an average 20,000-gallon pool on US city water at ~$5 per 1,000 gallons, about $100 — water-only. If your bill charges sewer per gallon too (~$12 combined), the same fill is ~$240 unless your utility grants the pool-fill sewer exemption.
- Why does my water bill charge sewer on pool water?
Because most bills assume water in = water out (down the drain), and charge the sewer share per gallon used. Pool fill water doesn't go to the sewer; many utilities will waive the charge if you ask. Sometimes it's automatic, sometimes you need a form or a separate fill meter — call before you fill.
- What's a CCF on my water bill?
CCF = hundred cubic feet = 748.052 gallons. Many US utilities bill in CCF rather than per 1,000 gallons. Confusing the two is a 7.5× error: $5 per 1,000 gal and $5 per CCF are very different rates for the same usage.
- Is trucked water cheaper than city water?
Almost always no. At a typical $0.10 per gallon delivered, a 20,000-gallon trucked fill is ~$2,000 — roughly 20× the ~$100 municipal cost. Trucked water is real when there's no municipal supply, a drought restriction, or a remote property, not when the tap works fine.
- How much does it cost to fill by pool size?
Linearly. At $5 per 1,000 gallons water-only: 10,000 gal = $50, 15,000 = $75, 20,000 = $100, 30,000 = $150. Double the gallons, double the cost.
- Does refilling after a drain cost the same as a fresh fill?
Yes — it's the same volume of water. A partial drain costs proportionally to the fraction you refill. (Ongoing evaporation top-off is a different thing entirely — a few inches a month, a few dollars; see the evaporation calculator.)
- Is the fill cost the whole pool cost?
No. A fresh fill needs startup chemistry balanced — that's the chemistry cluster (volume → chlorine → CYA → pH → alkalinity → calcium → LSI). Then the pump and heater (if you have one) run all season. The fill is a one-time line; the recurring costs are the budget.
- How do I lower the cost of filling my pool?
Three honest levers. (1) Ask your utility about the pool-fill sewer exemption — the big one, often over $100 on an average pool. (2) Fill during off-peak or lower-tier rate hours if your bill is tiered (some are). (3)Fill from the tap, not trucked, unless you can't — the tap is roughly 20× cheaper.
Related calculators
Next in Pool Water & Filling: Pool Fill Time Calculator.
Related across clusters: Pool Volume Calculator, Pool Evaporation Calculator.
All Pool Water & Filling calculators: browse the hub.