Boiler condensate trap: which trap fits Intergas, Nefit, Remeha, Vaillant or ATAG

Short answer: which condensate trap fits your boiler depends on the brand and series: the Intergas trap does not fit a Nefit and vice versa. A new trap costs € 10 to € 33. The trap sits below the heat exchanger, lets the condensate drain away and, as a water seal, stops flue gas from escaping. If it becomes blocked or cracks, you will find water under the boiler or the appliance will lock out. Below you will find, by brand, which trap and which seals you need, how to clean it and when you need a dry trap or a condensate pump. If the question is whether the water is condensate or heating water, first read Water under the boiler.

Why the condensate trap is so important

A condensing boiler cools the flue gases so far that the water vapour in them condenses; this produces a few litres of slightly acidic water a day. That water runs via the condensate tray to the trap and from there to the drain. The trap holds a column of water, just like the trap under a washbasin. That column is the only barrier between the flue side of the boiler and the room it hangs in. If the trap runs dry or is cracked, flue gas can leak into the room. That is why modern boilers run a trap-filling programme on start-up (Bosch then shows "-II-") and why the trap should be cleaned and filled at every service.

Blocked, cracked or loose?

What you see	Cause	What to do
Water dripping from the bottom of the boiler, pressure stays the same	Trap blocked or overflowing	Remove the trap, clean it, fill it and refit it
Water at the trap connection	Sealing ring or O-ring worn	Afdichtring vervangen, meestal € 12 tot € 24
Discoloured plastic, hairline crack, limescale ring	Trap itself worn	New trap
Smell of flue gas in the room, gurgling	Trap dry or water seal too low	Fill with water; if it comes back, check the drain
Boiler locks out, condensate drain or flue gas code	Drain blocked, water backs up into the boiler	Clean the trap and drain pipe
Boiler in the loft without a drain, water is standing	No natural fall	Condensate pump

Codes related to the condensate drain: Remeha E 425 (condensate drain blocked), Vaillant F.77 and AWB F.77 (condensate pump or flue gas flap), Bosch -II- (trap-filling programme active, not a fault). Many boilers have no separate code: a full condensate tray then ends in a fan or flue gas fault, because the water blocks the flue path.

Cleaning the trap: do it yourself or have it done?

If the trap hangs freely accessible at the bottom or side of the boiler, you can clean it yourself: switch the boiler off, remove the trap with a twisting motion (hold a container underneath), empty it, rinse it clean with water and a small brush, check for cracks, fill it with clean water and refit it with the sealing ring properly in place. Do this every year; it prevents most leaks. If the trap sits behind the appliance casing, it is part of the service by a certified gas engineer: opening the casing of a gas appliance and touching the flue path belongs there. Never refit the trap empty.

Which trap fits which brand?

The trap is specific to the brand and often to the series: the connection size on the condensate tray, the length and the position of the outlet differ. The parts below come from our catalogue, prices including VAT.

Brand	Part	Article number	Price
Intergas	Condensate trap (Kombi Kompakt HR)	8062701	€ 11.45
Intergas	Trap HRE	8062732	€ 9.95
Intergas	Trap L=235 HRE	8069082	€21.95
Intergas	Trap spigot, union nut, coupling KK	8062746, 8063041, 8063031	€ 6.95 to € 8.95
Nefit Bosch	Condensate trap (ProLine, TrendLine)	8029508	€ 19.95
Nefit Bosch	Condensate trap (TopLine, EcomLine)	8028865	€ 22.95
Nefit Bosch	Trap sealing ring, cap with gasket	8029375, 8024045	€ 15.95 and € 18.95
Remeha	Condensate trap (Tzerra, Calenta)	8010306	€ 22.95
Remeha	Trap Avanta after 2006	8016291	€ 24.45
Remeha	Condensate trap (Quinta, W series)	8012908	€ 32.95
Remeha	Trap gasket, 10 pieces, trap seal	8012626, 8016628	€ 18.95 and € 11.95
Vaillant	Connector trap/heat exchanger VHR, trap hose gasket	8054360, 8052026	€ 17.95 and € 15.95
ATAG	Trap latch i/S series, O-ring condensate tray/trap	8132182, 8131368	€ 25.95 and € 23.95
AWB	Trap cap, trap float, flexible hose	8077595, 8077594, 8077573	€ 14.95 to € 17.95
Bosch	Trap cover	8185225	€ 18.95
Ferroli	Trap Megadens/Megalux, trap Bluesense	8113211, 8110292	€ 22.95 and € 22.95

All traps and seals can be found under condensate traps, by brand for example under Intergas traps of ATAG traps. Always order the sealing ring as well: after years in acidic condensate it has almost always hardened.

Dry trap and condensate pump

A dry trap is a trap with a mechanical seal (a ball or membrane) instead of a water column. It is used where an ordinary trap can dry out, for example on the condensate drain of an MVHR (heat recovery ventilation) unit or an air conditioner that drains nothing for months, and in drains that cause odour problems. For the boiler itself, manufacturers specify their own trap; a dry trap belongs in the drain pipe after it, not in place of the boiler trap.

A condensate pump is needed if the boiler hangs lower than the drain or if there is no drain nearby in the loft. The pump collects the condensate in a small reservoir and pumps it away as soon as it is full. Vaillant and AWB report a faulty pump with code F.77. Pumps and accessories can be found under pumps.

Frequently asked questions

How much does a condensate trap for a boiler cost?

In our catalogue a trap costs € 9.95 (Intergas HRE) to € 32.95 (Remeha Quinta and W series); Nefit Bosch is € 19.95 to € 22.95. Order the sealing ring as well: after years in acidic condensate it has usually hardened.

How often should the boiler's condensate trap be cleaned?

Once a year, preferably before the heating season. A grey-brown sludge of soot and limescale collects in the trap and slowly clogs the passage.

Can boiler condensate go into the drain?

Generally yes: the condensate from a domestic boiler can usually be discharged directly into the indoor drainage system, but check your local regulations. Use plastic drainage materials; the water is slightly acidic and attacks metal pipes over time.

Why can I smell flue gas near the boiler?

Switch the boiler off and ventilate. A dry or cracked trap is one possible cause, but a flue gas smell can also come from the flue or the casing. Have the appliance checked by a certified gas engineer and do not use it until that has been done.

Will a universal trap fit my boiler?

Usually not properly. The connection to the condensate tray is brand-specific, and a trap with too low a water seal does not provide enough protection. Choose the part for your appliance type.