{"id":39694,"date":"2026-09-17T20:18:12","date_gmt":"2026-09-17T17:18:12","guid":{"rendered":"https:\/\/reoveemahutid.ee\/?p=39694"},"modified":"2026-09-17T20:26:04","modified_gmt":"2026-09-17T17:26:04","slug":"holding-tank-level-alarm","status":"publish","type":"post","link":"https:\/\/reoveemahutid.ee\/en\/holding-tank-level-alarm\/","title":{"rendered":"Sewage holding tank level alarms: how to choose the right one"},"content":{"rendered":"

A sewage holding tank (reoveemahuti<\/em>; in legal texts reovee kogumismahuti<\/em> \u2014 UK readers may know a sealed tank as a cesspool or cesspit) has no outlet, so once it is full the wastewater has nowhere to go. A holding tank alarm warns you in time to order the tanker that pumps it out (purgimine<\/em>). Choosing one comes down to how the signal reaches the people who must react, how the parts are powered, how far the radio must reach and how high the sensor hangs. This article covers wired versus wireless, range and batteries, installation, alarm signals and testing, and the two wireless alarms documented on Vesmaco’s site.<\/p>\n

Why a holding tank needs a level alarm<\/h2>\n

Unlike a septic tank (septik<\/em>), which passes settled liquid on to an infiltration field, a holding tank treats nothing and has no outlet. Under the Water Act (Veeseadus<\/em>) \u00a7 124, wastewater collected this way must go into a leak-tight (lekkekindel<\/em>) holding tank and be transported to a reception point (purgimiss\u00f5lm<\/em>). The Ministry of the Environment’s 2015 guide for rural wastewater systems adds that nothing may flow out or leak uncontrolled, and that the tank must not be left to overflow.<\/p>\n

The guide offers two ways to keep track: a dipstick (m\u00f5\u00f5telatt<\/em>), ordering the tanker once the level passes half the tank’s diameter, or a level sensor (nivooandur<\/em>; also called reoveemahuti andur<\/em> or t\u00e4ituvusalarm<\/em>), which it calls advisable. A sensor matters most where dipstick routines fail \u2014 water use that jumps with guests, a holiday home nobody checks, a riser under snow. To work out how long your tank lasts between emptyings, see How often should a sewage holding tank be emptied?<\/a><\/p>\n

The guide does not present the sensor as mandatory. Local holding-tank requirements come from each municipality’s rules for on-site wastewater handling (Water Act \u00a7 104(7)), and rules differ by municipality \u2014 check your local reovee kohtk\u00e4itluse ja \u00e4raveo eeskiri<\/em> to see whether it requires or recommends a level alarm. Vesmaco’s base kit \u2014 tank, emptying pipe, plastic cover and documents \u2014 has no alarm; the order drawing lists a high-level alarm as an option.<\/p>\n

Wired or wireless<\/h2>\n

Every alarm has a sensor in the tank and an alarm unit where someone will notice it; the difference is how the signal crosses the ground between them.<\/p>\n

\n\n\n\n\n\n\n\n\n\n\n
<\/th>\nWired alarm<\/th>\nWireless alarm (as on Vesmaco’s site)<\/th>\n<\/tr>\n<\/thead>\n
Signal path<\/td>\nCable in a buried protective conduit to an indoor unit<\/td>\nRadio from a transmitter in the tank or riser to an indoor receiver<\/td>\n<\/tr>\n
Groundwork<\/td>\nTrench to the building; cable entry through the riser wall<\/td>\nNo trench to the building<\/td>\n<\/tr>\n
Power<\/td>\nDepends on the product \u2014 ask<\/td>\nBattery in the transmitter; mains adapter for the receiver<\/td>\n<\/tr>\n
Distance<\/td>\nSet by the cable route<\/td>\n100 m stated; link test advised beyond 70 m or behind buildings<\/td>\n<\/tr>\n
Self-check<\/td>\nAsk whether a cut cable or dead sensor is reported<\/td>\nA lost link or flat battery raises a “No connection” alarm<\/td>\n<\/tr>\n
Adding it later<\/td>\nMeans digging to the house<\/td>\nTransmitter fits in the existing riser<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n

A wired alarm suits a tank close to the building while the trench is open; a wireless one suits a distant tank, buildings in between or a finished garden. Either way, ask where the alarm will be heard (a buzzer in an empty holiday home helps nobody), what happens when its own link or power fails, and whether the sensor can hang at the level you need.<\/p>\n

According to their manufacturer sheets, both alarms on Vesmaco’s site use a conductive sensor: the alarm triggers when liquid touches its electrodes at the height you set. They signal one level; the sheets describe no gauge showing how full the tank is in between. If you prefer a wired alarm, ask the supplier which products are available.<\/p>\n

Radio range, power and battery replacement<\/h2>\n

Range.<\/strong> The sheets give a 433.7 MHz LoRa link with a 100 m range and recommend a link test beyond 70 m or where buildings obstruct the signal. Fix the transmitter as high as possible in the tank or riser, above ground level if possible and not under a metal lid<\/strong>. Put the receiver indoors, preferably in the part of the building facing the transmitter and away from large metal surfaces. A power-boost mode can steady a weak link, but the sheets warn that it shortens battery life significantly \u2014 move the receiver first.<\/p>\n

Power.<\/strong> The transmitter runs on a 3.6 V AA lithium battery \u2014 not an ordinary 1.5 V AA cell \u2014 with a normal life of up to ten years, according to the sheets. The receiver plugs into a mains socket through a 230 V adapter, and the sheets mention no backup battery. Plan for the indoor alarm being off during a power cut or while a holiday home’s electricity is switched off; seasonal routines are in Sewage holding tanks for summer houses<\/a>. How the receiver behaves after a power cut and the transmitter’s operating temperature range for Estonian winters are worth asking the supplier before you buy; after any outage, check that the green OK lamp is lit again.<\/p>\n

Battery replacement.<\/strong> A flat battery triggers the “No connection” alarm, so it announces itself. Open the transmitter casing, change the battery minding the polarity, then repeat the link and sensor test below. Wear gloves: the transmitter sits above wastewater. Ask the supplier where to get replacement batteries and other spare parts.<\/p>\n

Installation: cable conduit and sensor height<\/h2>\n

Decide on the alarm before the pit is backfilled. Step 8 of Vesmaco’s installation guide says that when an overfill sensor is installed, a cable protection pipe (kaablikaitsetoru<\/em>) must be laid to the tank, a cable entry drilled in the riser wall and the sensor fitted according to its own instructions. The full sequence is in Sewage holding tank installation step by step<\/a>. With the wireless kits the sensor cable stays inside the tank, so their sheets need no cable to the house \u2014 but tell your installer your choice anyway: a conduit is easy to lay in an open trench and hard to add later. Ask the supplier whether the conduit is still needed with a wireless kit and where to fix the transmitter in your riser size.<\/p>\n

Sensor height.<\/strong> The sensor hangs on a 1.5 m cable below the transmitter; you set its height with the cable loop in the adjuster. Measure from the transmitter’s fixing point to the planned alarm level: riser height (500\u20131 000 mm as standard on Vesmaco’s order drawing, up to 1 500 mm with the optional D600 riser) plus the depth into the tank can exceed the cable. Where an EN 124 cover replaces the plastic cap for trafficked areas, ask what it is made of \u2014 the transmitter should not sit under metal. If the 1.5 m cable does not reach your planned alarm level, ask the supplier about the options before ordering.<\/p>\n

Alarm level.<\/strong> The space between the alarm level and the inlet pipe must hold what flows in while you wait for the tanker:<\/p>\n

reserve (L) = persons \u00d7 litres per person per day \u00d7 days until the tanker comes<\/code><\/p>\n

Use your own water-meter figure or the ministry guide’s planning range of 100\u2013150 L per person per day, and ask your emptying company how much notice it needs. Near the top of a horizontal tank each centimetre holds less volume than at mid-height, so the reserve shrinks fast as the sensor goes up:<\/p>\n

\n\n\n\n\n\n\n\n\n\n
Alarm level (share of diameter)<\/th>\nVolume filled<\/th>\nSpace left in a 5 m\u00b3 tank<\/th>\nDays for 4 people (400\u2013600 L\/day)<\/th>\n<\/tr>\n<\/thead>\n
50%<\/td>\n50%<\/td>\n2 500 L<\/td>\nabout 4\u20136<\/td>\n<\/tr>\n
60%<\/td>\n63%<\/td>\nabout 1 870 L<\/td>\nabout 3\u20134.7<\/td>\n<\/tr>\n
70%<\/td>\n75%<\/td>\nabout 1 260 L<\/td>\nabout 2\u20133<\/td>\n<\/tr>\n
80%<\/td>\n86%<\/td>\nabout 710 L<\/td>\nabout 1\u20132<\/td>\n<\/tr>\n
90%<\/td>\n95%<\/td>\nabout 260 L<\/td>\nless than 1<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n

Ideal horizontal cylinder; nominal volume treated as usable; space counted to the top of the tank. The inlet pipe enters lower, so the real reserve is smaller.<\/em><\/p>\n

Four people whose emptying company needs three days’ notice (an assumption \u2014 ask yours) need 1 200\u20131 800 L of reserve, so in a 5 m\u00b3 tank the sensor belongs at about 60% of the diameter or lower \u2014 close to the ministry guide’s half-diameter rule. The inlet height and the usable volume below the alarm level differ by model \u2014 check the drawing for your model and ask the supplier for the recommended alarm height.<\/p>\n

In short, from top to bottom: the transmitter is fixed high in the riser, the inlet pipe enters the tank, the reserve space lies between the inlet and the alarm level, and the sensor hangs at the alarm level; the receiver sits in the house within tested radio range.<\/p>\n

Alarm types and testing<\/h2>\n

According to the manufacturer sheets, the receiver shows three states:<\/p>\n

\n\n\n\n\n\n\n\n
Signal<\/th>\nTrigger<\/th>\nReceiver<\/th>\nWhat you do<\/th>\n<\/tr>\n<\/thead>\n
OK<\/td>\nUpdates from the transmitter every few minutes<\/td>\nGreen OK lamp lit<\/td>\nNothing<\/td>\n<\/tr>\n
Level alarm<\/td>\nLiquid reaches the sensor electrodes; 2-minute delay<\/td>\nRed lamp flashes, buzzer, relay 1<\/td>\nOrder the tanker; use as little water as possible<\/td>\n<\/tr>\n
No connection<\/td>\nNo update for about 30 minutes<\/td>\nOrange lamp flashes, buzzer, relay 2<\/td>\nCheck the transmitter for damage, radio obstacles and a flat battery<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n

Pressing Reset<\/strong> silences the buzzer, but the lamp stays lit until the cause is gone. If the level alarm comes much sooner than your calculation predicts, see Sewage holding tank filling too quickly?<\/a><\/p>\n

Relay outputs.<\/strong> Two potential-free relays (NO\/NC, max 24 V, 3 A DC) pass the level alarm (relay 1) and the no-connection alarm (relay 2) to an external device \u2014 a warning lamp in another building, say, or a separately bought text-message notifier. Choosing and wiring it is a job for an electrician. Each receiver reacts only to its own transmitter, so several tanks need several pairs. If you want a text-message notifier, ask the supplier whether a compatible one is available.<\/p>\n

Testing.<\/strong> In the sheets’ test mode the transmitter sends data without pauses:<\/p>\n

    \n
  1. Insert the battery, then hold the button on the transmitter’s circuit board until its indicator has flashed at least three times.<\/li>\n
  2. With the transmitter near its final position and the receiver plugged in where it will hang, a green OK lamp flashing about once a second means a good link; uneven flashing, or a lamp stuck on or off, means a weak one.<\/li>\n
  3. Dip the sensor in water or short its electrodes with a metal object: the red lamp, buzzer and relay 1 should react at once.<\/li>\n
  4. Test mode ends after about 10 minutes, or press the button for about a second.<\/li>\n<\/ol>\n

    Repeat the test after a battery change or moving the receiver, and add an alarm check to your routine \u2014 see Sewage holding tank maintenance: an owner’s checklist<\/a>.<\/p>\n

    Vesmaco’s range: Tank-Check RF-431 and Cesspool Alarm<\/h2>\n

    Vesmaco’s site offers a wireless filling alarm as a tank option and links two sheets: the Smartel Tank-Check RF-431<\/strong> and the Vesmaco Cesspool Alarm<\/strong>. Both name Smartel Electronics of Sipoo, Finland, as manufacturer; Vesmaco’s Smartel page says Vesmaco has been Smartel’s official representative in Estonia, Latvia and Lithuania since 2023 (see smartel.vesmaco.eu<\/a>, which also hosts the RF-431 guide<\/a> and the Cesspool Alarm guide<\/a>).<\/p>\n

    The two English sheets are word for word the same apart from the product name and contact details, so every figure in this article applies to both as documented. When ordering, ask which of the two comes with the tank’s alarm option, whether it arrives fitted or loose, and check the specifications against the sheet supplied with your unit.<\/p>\n

    The Smartel page also publishes an RF-431 declaration of conformity (radio equipment, low-voltage, EMC and RoHS directives; 4 May 2023) and RF-431 guides in five languages, Estonian and Russian included. The Cesspool Alarm file linked from reoveemahutid.ee opens on a Lithuanian page. If you need the conformity declaration or a guide in your language for the unit you buy, ask the supplier for it.<\/p>\n

    Frequently asked questions<\/h2>\n

    At what level should the alarm trigger?<\/strong> Low enough that the space up to the inlet pipe holds your household’s wastewater until the tanker comes. For four people with three days’ notice in a 5 m\u00b3 tank, that means about 60% of the diameter or lower; ask the supplier for your model’s recommended height.<\/p>\n

    How far does a wireless sensor reach?<\/strong> The sheets state 100 m and advise a link test beyond 70 m or where buildings stand in the way. Move the receiver before using power boost, which shortens battery life significantly.<\/p>\n

    Can it be retrofitted to an existing tank?<\/strong> Vesmaco’s Smartel page says the RF-431 can be installed in an existing cesspool or a tank from any manufacturer. Check for a fixing point high in the riser and not under metal, that the 1.5 m cable reaches your alarm level, and that the receiver has a socket within tested range. An alarm will not make a leaking tank tight.<\/p>\n

    Add an alarm to your tank quote.<\/strong> In the quote form<\/a>, name the tank model or volume, add the level alarm, and say roughly how far the tank will be from the building where the receiver will hang and what stands in between \u2014 or call +372 641 8550<\/strong>; the site says replies usually come within 2\u20133 days. Vesmaco manufactures the tanks and provides consultation, design and delivery in Estonia; fitting the tank and the alarm is up to your installer.<\/p>\n

    Sources<\/h2>\n