100mm In-line Extractor Fan Vent Back Draught Shutter With One Spring And Two Flaps

Having an extraction system in my bathroom I was suffering cold air entering during windy times when the fan was not running. Sadly my fan did not have a non return valve built in so a retrofit unit was the solution. This unit is designed to be a push fit to the inside diameter of 4 inch rigid plastic pipe. In my installation like many others I simply have 4" flexible pipe fitted onto the outlet pipe manifolds of the extractor fan. Therefore this unit is not sized to push inside or outside the fan manifolds as standard so a little adaption is required that may be outside the ability of anyone without suitable tools. I filed a slight bevel to the outside of this unit and then using a Dremmel and sanding tip I sanded a slight bevel inside the fan manifold so the unit just slid inside enough to be secure and taped up with duct tape to be sure. The flexible duct did fit over the unit and was again held secure and sealed with duct tape and all now works well. Some people have made note of the single spring which lightly holds the vanes closed perhaps being too weak. I would point out the design of this shutter is meant to be light so that it does not reduce the fan output force which is usually not that strong especially if it is in longer runs of pipework. If the fan is not running and an incoming draught is present the spring will be strong enough to ensure the vanes move closed. Of additional note, the vanes have small pieces of foam to cushion the closing and because there is no plastic on plastic contact this helps to keep the action quiet It may seem such a simple plastic device is expensive but it solves the backdraught problem and is maintenance free. Although I did not see it specified, I would suggest this unit is best installed in horizontal pipe runs, Vertical sections may have too much gravitational effect to work well without reducing fan output.

This is a lightweight plastic valve but it will do the job. It fits nicely onto a spigot on the discharge side of the Manrose ceiling fan I have in the bathroom ceiling. One spring is fitted. This provides just enough force to restore each of the two flaps to the closed position. The spring appears to be mild-steel and will eventually corrode in the humid exhaust air from the bathroom. I fitted the valve with the axis vertically so that the flaps are horizontal. As a result the flaps tend to clatter open/shut when there are strong winds outside. I fitted small strips of self adhesive foam on the seats under the flaps to cushion their landing and also put small pieces of duct tape on the upper side of each flap to provide material damping. The flaps now work well and are silent. Good value for the price if you can be bothered to solve the clattering problem.

Works fine. Ignore the comments about the spring being too weak. It’s not supposed to close on its own. It opens fully when the fan is on and partially closes when the fan turns off. It then closes fully if there is a draught. This is how it’s designed to work. It’s fitted with foam on the back of the flaps to stop them rattling which seems to work fine too.

Good news and bad news. Good news - Today is windy and the draught coming into the bathroom is reduced a lot, but not quite 100% stopped. The extractor fan continues to extract. There is no noise increase. The tube of the Backdraught Shutter fits inside the flexible hose which then goes to the vent in the soffit. A cable tie / zip tie of suitable length wraps around the flexible hose and, pulled tight, gives a secure seal on the plastic tube. Bad news - I have a Manrose extractor fan, less than 6 months old. It's screwed to a joist timber in the loft. It says HDCWK SLKTC SKU 148825 on the side of it. It is described as 4" / 100 mm. The Backdraught Shutter I bought is also Manrose 4" / 100mm so I would expect them to be compatible. I would expect the Backdraught Shutter to fit into (or perhaps over) the extractor fan outlet tube. But no - they are both the same diameter so they butt up to each other. I used duct tape to join the 2 together. Without the tape they would never join. They even put a slight reduction in the outside diameter of the Backdraught Shutter as if it should fit into the extractor fan tube but it does not. Also the spring is weak, but as the backdraught blows along the hose from outside the house the natural pressure is to push the flaps closed. But they do not form a perfect seal - 1 of them moves very easily, the other semi-circular flap seems to be a tiny fraction too big for the circular tube. I suspect the extractor fan struggles to blow this half open, but as the other half opens easily the moist air is blown out. I was tempted not to install, and return the Backdraught Shutter but the location is in the far corner of the loft and having made 2 trips there and got it assembled so it works I decided to 'cut my losses' and make the best of it. A trickle of ventilation in a bathroom is no bad thing. But I am disappointed with Manrose - it seems to be a complete lack of thought on their part. Final piece of info - I don't see how this unit could work in a vertical position. The spring is too weak to shut the flaps even when the tube is horizontal. The spring is not strong enough to overcome gravity. I ought to do the other bathroom. I'll buy a different style of Backdraught Shutter!

Exactly what I wanted

La valvola fa il suo dovere, le 2 alette sono contrastate da una molla molto debole, funziona quindi adeguatamente se posizionata in orizzontale. Se posizionata in verticale potrebbe non operare correttamente perchè le alette per deboli flussi d'aria potrebbero rimanere chiuse o se girata al contrario portrebbero rimanere sempre aperte sotto l'azione del proprio peso. La chiusura è buona anche se non ermetica in quanto piccole fessure consentiranno comunque a poca aria di circolare anche nel verso contrario alla valvola. Quando la valvola chiude per un flusso d'aria forte in senso contrario si sente un rumore di scatto abbastanza fastidioso sopratutto di notte con aperture e chiusure frequenti causate dal vento. Il problema si può risolvere incollando un pezzetto di elastico di gomma sulla zona di battuta della croce al centro in modo da annullare quasi completamente il rumore. Qualcuno lamenta una molla troppo debole, in effetti in assenza totale di flusso d'aria le alette potrebbero rimanere anche aperte o semi aperte. Questo non mi pare un problema in quanto la valvola deve impedire un ritorno di aria, al mimino flusso contrario le alette si chiudono istantaneamente. Una molla di contrasto così debole è appropriata per consentire l'apertura completa anche con un flusso in uscita dalla valvola molto debole. Per il prezzo, la metà almeno di una valvola di metallo, mi sembra che non si possa chiedere di più.

Le ressort est très léger .... Si on le penche un peu, le ressort n'arrive pas à fermer le clapet. Il n'y à aucun joint d'étanchéité.

Just as promised

Esta muy mal descrito, no es un ventilador. Es una especie de válvula antiretorno, muy económica, muy sencilla, parece frágil... Pero evidentemente no vas usarlo en una instalación industrial con aire a 6 bares de presión. Este antiretorno lo he instalado en posición vertical justo después del extractor (en el baño) de hecho los he pegado... Pues bien esta visita tan simple evita que a mi baño entren los malos olores de las tuberías de centro de edificio. D Desde que lo he instalado ya no entran esos olores desagradables de los baños de musique vecinos. Este cacharro es una maravilla. Personalmente creo que deberían mejorar el sistema con 2 muelles en lugar de uno e instalar una junta, mejorar la estanqueidad y aunque costará 3 veces más, creo que será algo ideal e indispensable en todo hogar. Pero ojo cuando se instale se debe hacer a la salida del extractor, para que el aire que es impulsado abra las compuertas o pestañas de esta válvula antiretorno y además se debe instalar en posición vertical, para que cuando se apague el extractor, la gravedad haga que se cierre la válvula por su propio peso

Scarsa la tenuta della molla, non sufficiente a chiudere, a riposo, il tubo. Pensavo mancasse una molla: c'e l'alloggiamento per un'altra dello stesso tipo e pensavo si fosse smontata. la foto del prodotto pubblicata, ne mostra solo una ed evidenziata. Ho risolto il problema montando un elastico di tenuta, fissato con due viti sulle palette che si muovono! Ho scelto di non restituire il prodotto ma, appunto, di modificarlo per averne il funzionamento corretto!