+372 641 8550
Price inquery

5 m³ or 10 m³ sewage holding tank: which size should you choose?

You have settled on a sewage holding tank (reoveemahuti; in legal texts reovee kogumismahuti) and the shortlist is down to two volumes. A holding tank only stores wastewater until a tanker pumps it out (purgimine) — no treatment, no outlet; UK readers may know such a sealed tank as a cesspool or cesspit. So the 5 m³ vs 10 m³ holding tank decision does not change how much wastewater you pay to have removed. It changes how often the tanker comes, whether one visit empties the tank, and how much ground and transport the tank needs. The comparison below uses Vesmaco’s own model data.

The two sizes side by side: Vesmaco model data

Vesmaco makes each volume in two diameters, so the choice is really among four horizontal fibreglass (GRP) tanks. Values as displayed in the model table:

MK-5 D1100 MK-5 D1400 MK-10 D1400 MK-10 D1600
Diameter 1100 mm 1400 mm 1400 mm 1600 mm
Length (about) 5.7 m 3.6 m 6.7 m 5.3 m
Weight 300 kg 290 kg 500 kg 480 kg
Safety zone on a green area* 7.7 × 3.1 m 5.6 × 3.4 m 8.7 × 3.4 m 7.3 × 3.6 m

*Vesmaco’s installation guide: on a green area, accidental driving over the tank must be excluded in a zone 1 m larger than the tank in every direction — here (length + 2 m) × (diameter + 2 m). Lengths are approximate, so for exact dimensions check the drawing for your model.

Doubling the volume does not double the tank: the MK-10 D1600 is about 1.7 m longer than the MK-5 D1400, 200 mm larger in diameter and 190 kg heavier, while the MK-10 D1400 keeps the 5 m³ diameter and adds about 3.1 m of length. The site lists one base kit for the whole range (tank, emptying pipe, plastic cover, documents); options are marked on the order drawing, and the drawings for these four models (rev. B, 15.08.2025) carry the same option list, including a maximum inlet depth of 1500 mm. For diameter families and reading the drawing, see Sewage holding tank dimensions and drawings.

The same household, two emptying rhythms

The method, explained in full in What size sewage holding tank do you need?:

days between emptyings = usable volume (L) ÷ (persons × litres per person per day) emptyings per year = 365 × occupancy share ÷ days

Assumptions: the ministry guide’s planning range of 100–150 L of wastewater per person per day (your own water-meter data is better); permanent occupancy (share = 1); usable volume = nominal volume, although the real alarm level leaves a reserve, so the usable volume is somewhat below the nominal volume — check the drawing and the alarm height for your model.

Household Wastewater per day 5 m³: days · visits/year 10 m³: days · visits/year Removed per year, either tank
2 people 200–300 L 17–25 · 15–22 33–50 · 7–11 73–110 m³
4 people 400–600 L 8–12.5 · 29–44 17–25 · 15–22 146–219 m³
6 people 600–900 L 5.5–8 · 44–66 11–17 · 22–33 219–329 m³

The last column is the one to remember: a bigger tank does not remove a litre less — it halves the number of visits. The ministry guide’s benchmark for a four-person family living permanently is at least 5 m³, emptied about once a week — a minimum, not a target. With 10 m³ the same family sees the tanker about every 17–25 days. More examples: How often should a sewage holding tank be emptied?

One situation has a legal floor. If you are in a sewage collection area (reoveekogumisala) of 2000 population equivalents or more and cannot connect because public sewerage is missing, the water company must organise emptying (purgimisteenus) on request, and the Public Water Supply and Sewerage Act (ÜVVKS) § 47(7) (English translation; only the Estonian text has legal force) requires a leak-tight tank holding at least two weeks’ wastewater: on the planning range 2.8–4.2 m³ for two people, 5.6–8.4 m³ for four and 8.4–12.6 m³ for six, so 5 m³ is too small for four. The rule is explained in full in What size sewage holding tank do you need?; elsewhere, your municipality’s on-site wastewater rules (reovee kohtkäitluse ja äraveo eeskiri, Water Act § 104(7)) may set their own requirements — check them before ordering.

Will one tanker visit empty it?

The ministry guide notes that small tankers hold 4–5 m³ and the largest about 10 m³, and advises checking what is available locally.

  • 5 m³ matches the small tankers, although a 4 m³ truck cannot take a completely full tank in one load.
  • 10 m³ needs the largest class of tanker — and access that suits it. If local operators run only 4–5 m³ trucks, a full tank takes two loads and the larger tank’s advantage shrinks or disappears.

Ask local emptying companies for the tanker’s capacity, whether they charge per visit or per m³, and whether a second load counts as a second visit. Then annual cost = emptyings per year × your local price per visit. Charged per visit, 10 m³ roughly halves the bill, provided one visit empties the tank. Charged per m³ — as under ÜVVKS § 48(2), where the § 47 service costs the same per-m³ charge as for customers connected to public sewerage, plus any monthly subscription fee — tank size barely matters.

In the ground and on the lorry

Depth. The ministry guide says installation depth follows the building’s sewer pipe; Vesmaco’s guide adds a compacted sand bed of at least 20 cm. The rest is diameter: at the same inlet depth a D1600 tank sits deeper than a D1400, while the MK-10 D1400 needs no more depth than the MK-5 D1400 — only a longer pit.

Groundwater. An empty tank lying fully below groundwater is pushed up by the weight of the water it displaces: roughly 5 t for 5 m³ and 10 t for 10 m³ (fresh water, 1000 kg/m³; soil cover ignored), against a tank weight of 290–500 kg. Vesmaco’s guide anchors tanks with textile straps to a reinforced-concrete slab or blocks sized by a certified designer. The optional anchoring straps on the order drawings number 4 for the MK-5 D1400 and 6 for the MK-5 D1100, MK-10 D1400 and MK-10 D1600.

Backfill and delivery. The guide requires backfilling in 30 cm sand layers while adding water to the tank, so a 10 m³ tank needs about twice the water and noticeably more sand. On the lorry it is 3.6–5.7 m and 290–300 kg against 5.3–6.7 m and 480–500 kg. Whichever size you choose, prepare the site before delivery: vehicle access to the plot, a firm surface, a clear space to set the tank down, and unloading agreed with the supplier in advance.

Between and beyond: 6–9 m³, 12–15 m³ or two tanks

The choice is not binary: Vesmaco lists 6, 7, 8 and 9 m³ models in D1400 and D1600. An 8 m³ tank gives four people 13–20 days (8000 L ÷ 600 or 400 L per day); the MK-8 D1600 is about 4.3 m long and weighs 400 kg.

Above 10 m³ come the MK-12 D1600 (about 6.3 m, 560 kg), MK-15 D1600 (7.8 m, 750 kg) and MK-15 D2000 (5.2 m, 800 kg). Four people fill 15 m³ in 25–37 days, but a tank larger than the biggest local tanker cannot be emptied in one visit, so volumes this large are mostly considered as a buffer for peak loads, for example at holiday rentals and campsites. Where one long pit does not fit, the guide allows several tanks at least 50 cm apart.

A quick way to decide

  • 5 m³ tends to fit one or two permanent residents or seasonal use, areas where tankers hold 4–5 m³, short pits, and per-m³ charging.
  • 10 m³ tends to fit three or more permanent residents, cases where the § 47 two-week volume exceeds 5 m³, and areas where a 10 m³ tanker charges per visit.
  • 6–9 m³ is worth a look when your numbers fall in between.

Frequently asked questions

Can I start with 5 m³ and add a second tank later? Technically yes: Vesmaco’s guide covers several tanks at least 50 cm apart. It means a second excavation and new pipework, and since installing a holding tank requires a building notice (ehitusteatis, Building Code Annex 1) and a use notice (kasutusteatis, Annex 2), expect to file both again for the extension — confirm with your municipality. Ask the supplier how a second tank would be connected to the first before you plan on it.

How do I work out whether the bigger tank pays for itself? Payback in years = extra cost of buying, delivering and installing the 10 m³ tank ÷ (visits saved per year × local price per visit). Take the visits saved from the table above and the prices from your own quotes: ask for both tank sizes on the same basis and check what each quote includes, such as delivery. If emptying is charged per m³, there is little to pay back.

Which size suits a summer house? For two people, 5 m³ lasts 17–25 days of actual occupancy; at 60 days of use a year that is 2.4–3.5 tankfuls (60 ÷ 25 = 2.4; 60 ÷ 17 = 3.5), so about three or four tanker visits if the tank is emptied at the end of the season. 10 m³ is worth considering for large families, frequent guests or rental use. For very small flows, see 2–3 m³ sewage holding tanks: when is a small tank enough?

Ask for quotes on both sizes. Send Vesmaco the number of people and how the property is used, the inlet depth, the groundwater situation and whether vehicles will pass over the tank, and ask for quotes on a 5 m³ and a 10 m³ model with the matching drawings. Vesmaco manufactures the tanks, advises on the choice and delivers across Estonia; installation and emptying stay with your installer and your local emptying company. Use the quote form or call +372 641 8550.

Sources