+372 641 8550
Price inquery

Sewage holding tanks for summer houses: planning for seasonal use

A summer house (suvila) is busy for a few weeks and silent for months, and that rhythm decides how its wastewater is best handled. If you are sorting out summer house sewage in Estonia and your road has no mains sewerage, a sealed sewage holding tank (reoveemahuti; in legal texts reovee kogumismahuti; UK readers may know it as a cesspool or cesspit) copes well with such use: it stores wastewater until a tanker pumps it out (purgimine), treats nothing and has no outlet. The short answer: size it by person-days and your longest stay, make sure a tanker can reach it, and do not leave it empty over winter where groundwater is high.

Why a holding tank suits a house that stands empty

The Ministry of the Environment’s 2015 guide to on-site wastewater systems names private houses and summer houses as fits for a holding tank where, among other cases, water use is small or periodic. Its planning tables mark seasonal use as applicable to a holding tank and as “not possible” for biofilm and activated-sludge treatment plants. A holding tank has no treatment process, so nothing needs restarting in spring. The drawback is just as plain: every litre that goes in leaves by tanker, so the running cost is emptying.

Whether a holding tank is required or one of several options depends on whether the plot lies in a sewage collection area (reoveekogumisala; Water Act § 124) and on the municipality’s on-site wastewater rules (§ 104(7)), which may add a setback (kuja) or proof of emptying. Check the rules of the municipality where the summer house stands, not where you live. Installing the tank needs a building notice (ehitusteatis) through the Building Register at least 10 days before work starts, then a use notice (kasutusteatis).

Occupancy-days arithmetic: count person-days, not months

A tank does not fill by the calendar; it fills by people being there.

season volume (L) = person-days × litres per person per day tanker visits per season = season volume ÷ usable tank volume

Worked example. A family of four uses the house on 16 weekends (32 days) and for a three-week holiday (21 days): 53 days, an occupancy share of about 0.15, or 4 × 53 = 212 person-days. At the ministry guide’s planning range of 100–150 L of wastewater per person per day, that is 21.2–31.8 m³ a season. Living there permanently, the same family would produce 146–219 m³ a year.

The assumptions: 100–150 L is a planning figure for permanent living; a summer house may use less, or more with a sauna and frequent guests. Sauna water piped to the same tank counts as inflow; a sauna building with its own drain is a separate calculation — see collecting sauna wastewater. Your own water-meter data beats any planning figure; with an unmetered well, the first season’s emptying receipts show how many cubic metres were really taken away. Usable volume is taken as nominal volume; in practice the volume usable up to the alarm level is somewhat below nominal, so real intervals are somewhat shorter — check the drawing and alarm height for your model.

Size for your longest stay, not the seasonal average

The seasonal total gives the budget: annual cost = visits per season × your local price per visit (ask whether the charge is per visit or per cubic metre). Tank size is decided by something else: how long the tank lasts while everyone is there.

Tank Four people staying (400–600 L/day) Weekends only (800–1200 L per weekend) Visits in the example season
3 m³ 5–7.5 days about 2.5–3.75 weekends about 7–11
4 m³ about 6.7–10 days about 3.3–5 weekends about 5–8
5 m³ about 8–12.5 days about 4–6 weekends about 4–6.5
6 m³ 10–15 days 5–7.5 weekends about 3.5–5.5

Real visits round up, because nobody waits for the last litre. In the three-week holiday the example family produces 8.4–12.6 m³, so even a 5 m³ tank that starts the holiday empty needs one or two tanker visits during it and another soon after; six people fill it in about 5.5–8 days. The ministry guide advises ordering the tanker when the level passes about half the diameter — and ask how quickly the emptying company can come in July.

Two limits apply. The guide notes that small tankers hold 4–5 m³ and the largest about 10 m³: a tank bigger than the tanker that can reach you cannot be emptied in one visit. And where § 47 of the Public Water Supply and Sewerage Act applies — collection areas of 2000 p.e. (population equivalents) or more without public sewerage — the tank must hold at least two weeks’ wastewater (§ 47(7)); ask the municipality or water company how they assess that volume for a seasonally used house.

Up to 5 m³, Vesmaco’s models come either long and shallow (for example MK-5 D1100, about 5.7 m long) or shorter with a deeper pit (MK-5 D1400, about 3.6 m); the 6 m³ models have a diameter of 1400 or 1600 mm: see the model table.

Narrow garden-cooperative roads: can the tanker reach you?

Many summer houses stand in garden cooperatives (aiandusühistu) whose lanes were laid out for cars, not trucks. The ministry guide says tanker access must be guaranteed in every season. Before fixing the tank’s position, ask the emptying company that serves the area:

  • which of its tankers can use your road, and what volume it carries;
  • what hose length it brings — this sets how far from the road the emptying riser may stand;
  • whether the road is passable in the spring thaw and late autumn;
  • whether you must be present when it comes.

The answers usually push the tank towards the road. Three things push back. The municipality may set a kuja from boundaries, buildings and wells — there is no national distance for holding tanks. Vesmaco’s installation guide asks for a safety zone 1 m larger than the tank in every direction on green areas. And the corner by the gate is often where cars park: the ministry guide says a holding tank must not go under a road or parking area and the tanker must be kept off it, while Vesmaco’s guide allows a trafficked area only with a reinforced-concrete slab (at least 15 cm thick, 50 cm above the tank, 50 cm wider all round) and a suitable hatch class — a designer’s job. Keeping cars off is simpler.

The tank arrives by the same road — an MK-5 D1400 is about 3.6 m long and weighs 290 kg — so describe the road in your enquiry and agree the unloading with the supplier in advance: the delivery vehicle needs access, a firm surface and a clear space to set the tank down. More in tanker access for holding tank emptying.

Closing for winter: neither brim-full nor pumped dry

Pumping the tank dry when you lock up in October feels tidy; where groundwater is high it is the wrong habit. The ministry guide calls a concrete slab and anchoring essential with high groundwater precisely so that an empty or half-empty tank is not lifted and damaged. An MK-5 D1400 weighs 290 kg, but surrounded by groundwater its 5 m³ volume displaces about five tonnes of water. Groundwater is often highest in the autumn rains and the spring thaw — when nobody is there to notice.

  • Settle anchoring at installation. Vesmaco’s guide describes a reinforced-concrete slab (or blocks in stable soil) sized by a certified designer, and textile straps tensioned with the tank a quarter full of water. Judging groundwater on your plot is covered in holding tanks and high groundwater.
  • Do not order a closing emptying by reflex. One way to avoid an empty tank is to let the last weekends’ wastewater stay in as ballast — before relying on it, ask the supplier what level to leave for your tank and site and how to protect tank and riser from frost. Leave room as well: New Year visits add wastewater when the tanker may not get down an unploughed lane, and a tank must never overflow.
  • Note the level when you lock up and when you reopen. In an unused, leak-tight tank it should not have moved. A rise means meltwater or groundwater is getting in, and you will pay to truck it away; a fall points to a leak.
  • Mind frost and the alarm. The ministry guide says pipe and tank must be insulated from above where they lie shallower than about 1.3 m. A level alarm helps during stays, but the Smartel Tank-Check RF-431 receiver signals indoors with a light and buzzer, which nobody hears in a locked house, and it plugs into a mains socket through an adapter, so it is off while the electricity is switched off. It has two relay outputs for external signalling; if you want an alarm to reach you while the house is empty, compare the datasheets and ask the supplier what can be connected to them.

Frequently asked questions

Can I choose a smaller tank because we are only there in summer? Only if your longest stay allows it. Seasonal use cuts the number of tanker visits, not the speed at which the tank fills while you are there: four people fill 3 m³ in 5–7.5 days.

Can the rural household grant (hajaasustuse programm) pay for a summer-house tank? Not under the current regulation: § 8(1) excludes households not used year-round as the applicant’s permanent residence since 1 January of the application year. Terms can change between rounds, so check the current conditions with RTK or your municipality. What the grant does cover is explained in the hajaasustuse programm and holding tanks.

We may move in permanently one day — should we size for that now? If it is a real plan, yes: a buried tank cannot be enlarged. The ministry guide’s benchmark for four people living permanently is at least 5 m³, emptied about weekly; see holding tanks for year-round homes.

Request a quote for your summer house. Tell us the number of people, your season (weekends and longest stay), the inlet depth, whether groundwater can be high and what the access road is like, and we will suggest matching models with their drawings. Use the quote form or call +372 641 8550. Vesmaco manufactures and delivers the tanks; installation is done by your installer and emptying by your local emptying company.

Sources