Neutralisation box for the acidic condensate of gas or oil condensing boilers: from one 35 kW wall-hung boiler to a 1500 kW cascade. Condensate from a condensing boiler is acidic, with a pH below 5. In the neutralisation box it flows through a bed of calcite (natural calcium and magnesium carbonate) that binds the acid, so neutral water goes to the sewer and drain pipes, inspection pits and sewers are not attacked. Ventichim, flue systems wholesaler in Zandhoven (Belgium), supplies the boxes with the first calcite filling and pH paper, and the refills separately.
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Why we recommend neutralising
- Longer life for drains and sewers: acidic condensate with a pH of 2 to 5 attacks cement mortar, concrete, cast iron and metal, every single day. Neutral water does not.
- It adds up: a family home produces 500 to 2000 litres of acidic condensate a year, a cascade many times more. It all runs through the same pits and pipes.
- In line with Buildwise advice: TV 235 recommends in principle neutralising condensate before it enters the sewer.
- Small cost, peace of mind: a box with a calcite filling costs a fraction of a repair to the drain or sewer, and the pH paper shows you that it works.
Which neutralisation box do you need?
Choose by the total nominal output of all boilers draining into the box; for a cascade, add the boilers together. Between two sizes, take the larger one: more calcite lasts longer.
| Output | Code | Type | Dimensions (l x w x h) | Connection | Filling | Refill |
|---|---|---|---|---|---|---|
| up to 35 kW (one wall-hung boiler) | NEUT72702 | in-line neutralizer on the condensate pipe | G3/4" with ø20 mm hose tail, in and out | pearls | NEUT727R (5 packs) | |
| up to 120 kW | NEUT1338 | box with lid | 300 x 200 x 185 mm | inlet DN40, outlet DN20 | 5 kg calcite | NEUT1339 |
| up to 200 kW | NEUT1323 | box with lid | 400 x 300 x 235 mm | inlet DN40, outlet DN20 | 7 kg calcite | NEUT1328 |
| up to 350 kW | NEUT2251 | box with lid | 400 x 300 x 235 mm | inlet DN40, outlet DN20 | 10 kg calcite | NEUT1301 |
| up to 1500 kW | NEUT2252 | box with lid | 600 x 400 x 235 mm | inlet DN40, outlet DN20 | 25 kg calcite | NEUT2254 |
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How a neutralisation box works
The condensate enters through the DN40 inlet and a perforated distribution tube, flows through the calcite and leaves the box through the DN20 outlet to the sewer. The calcite slowly dissolves and neutralises the acid; only a little carbon dioxide is released. The box works without power, by gravity. The neutralizer up to 35 kW works the same way, as a transparent filter housing with neutralising pearls in the condensate pipe of one wall-hung boiler, for a flow of up to 3 litres per hour; the window shows how far the pearls are used up.
How to install the neutralisation box
- Choose the size by the total output (table above) and order a refill straight away for the first service.
- Place the box level on the floor, lower than the condensate drain of the boiler or boilers, so the condensate flows in by gravity. The neutralizer up to 35 kW hangs on its wall brackets, vertical or horizontal, at least 180 mm below the condensate drain of the boiler.
- Connect the boiler condensate drain, after the boiler siphon, to the inlet and the outlet to the sewer. If the sewer is higher than the box, fit a condensate pump after the box.
- Fill the box with the supplied calcite and close the lid with its safety catch.
- Measure the pH with the pH paper at commissioning and then every six months.
Maintenance and refills
The calcite is used up as it neutralises acid. When the pH of the water after the box drops below 6.5, replace the whole filling and rinse the sediment out of the box. In practice this is about once a year, sooner with heating oil or a cascade that runs a lot. Order the refill in the weight of the original filling: 5 kg (NEUT1339), 7 kg (NEUT1328), 10 kg (NEUT1301) or 25 kg (NEUT2254). For the neutralizer up to 35 kW, replace the pearls every 8 to 12 months with the 5 packs NEUT727R; two neutralizers in series last longer.
Frequently asked questions about condensate neutralisation
Is a neutralisation box mandatory in Belgium?
There is no legal obligation, but we always recommend a neutralisation box. Buildwise (formerly BBRI, Technical Information Note 235) advises in principle neutralising condensate before it enters the sewer, and the sewer rules forbid substances that make sewage toxic or dangerous. Acidic condensate eventually attacks everything it runs past; neutralising it extends the life of drains, pits and sewers. For cascades, larger installations and heating oil, a box is a must for us.
Can condensate run through a copper, zinc or steel pipe?
No. Condensate has a pH of 2 to 5, depending on the fuel, and attacks copper, brass, bronze, steel and zinc; concrete and masonry dissolve in it. Use plastic (PVC, PP, PE) or stainless steel for the condensate drain, for every fitting too: the condensate drain is checked during the gas inspection. If the condensate then flows through an old cast iron or concrete sewer, a neutralisation box protects those pipes.
Can condensate go into the gutter or onto the roof?
No. Never let condensate run over a metal roof, into a zinc or metal gutter or over concrete: the acid attacks these materials and an outside drain freezes in winter. Connect to the indoor drainage, at a point where household waste water flows regularly, with a siphon with an open connection. A neutralisation box goes between the boiler and that drain and never replaces the connection.
Why is condensate acidic?
When the flue gases condense, carbon dioxide dissolves in the water and forms carbonic acid; with heating oil, sulphur oxides are added and form sulphuric acid. A family home produces 500 to 2000 litres of acidic condensate a year (BBRI Digest 10.1).
How long does a calcite filling last?
That depends on how much condensate the boilers produce. Count on about one year and check the pH every six months. The pearls of the neutralizer up to 35 kW are replaced every 8 to 12 months.
How do I measure the pH?
Dip a strip of pH paper in the water coming out of the box and read the pH; each box comes with 4 strips. As long as the pH is 6.5 or higher, the filling works: that is the target value of TV 235.
Is the box suitable for an oil-fired boiler?
Yes, for gas and oil condensing boilers. Oil condensate is more acidic, so the calcite is used up faster: check the pH more often. With heating oil, TV 235 also recommends an activated carbon filter before the neutralisation.
Which box fits a cascade?
Add up the nominal output of all boilers and choose the next box up: two 100 kW boilers (200 kW) on NEUT1323, four 80 kW boilers (320 kW) on NEUT2251. See also our cascade systems.
What is the delivery time?
The neutralisation boxes and refills are not in stock: delivery 2 to 3 weeks after ordering.
Ordering and delivery
You can order directly in the webshop. Prices in the webshop are recommended retail prices for private customers; installers with a login see their net price. Not sure about the size? Email the number of boilers and their output to info@ventichim.be or call +32 3 349 71 30. Not in stock: delivery 2 to 3 weeks after ordering.
