Replacement bathroom extractor fan

[Norfolk Broad]

Hello again, everyone.

It's been a while, but I have my next project that I would appreciate some input, please.

Background:
- First floor flat, with access to loft space.
- Internal shower room with no window, no external walls.
- Existing Manrose extractor fan is located in the ceiling above the toilet, venting approx. 3 metres directly upwards through a 110 mm PVC pipe.
- In certain weather conditions, mainly north wind, the fan will drip (brown) water onto the toilet!
- Occasional debris (rusty-looking particles) also drop through the fan and into the bathroom.

My neighbour in the next door flat replaced his fan, but also (I understand) replaced the vertical tubing as well.

I want to do something similar but can't help thinking I should use the opportunity to use a different type of fan (inline centrifugal), as well as relocate the inlet over the shower, where more steam is generated. Any condensation could be trapped and directed to the SVP via a running trap. Debris will also collect at the bottom of an S-bend/U-bend.

A couple of diagrams explain the current situation, and my proposed plan.

- I plan to use rigid ducting, not flexible ducting.
- The horizontal run between the fan and the S-bend/U-bend is approx. 1 metre.

I'm not afraid to spend approx. £100 on a decent air-shifting fan - I'd fit a jet engine if I thought it would help!
But questions I have are:
- Is the proposed pipe run too tortuous? Will the labyrinth restrict the flow too much?
- Should the fan be located somewhere else?
- Should I also add a backdraft shutter between the fan and the U-bend?

Any advice gratefully received, thanks.

 

[Taylortwocities]

As there is no window you will need a timer fan (ie runs on after the light goes off). Is the existing a timer fan?
The duct plan looks great. Smooth is better. Good idea to put the outlet above the shower
You need a fan with a decent bit of welly. These are good, in my experience https://www.tlc-direct.co.uk/Products/SLTDK160T.html but your budget may make it out of court?
That would put you more in this area https://www.tlc-direct.co.uk/Products/ADAV100T.html

Backdraft shutter a good idea, if your outlet doesnt have one.
Dont forget to provide a way to let enough air into the room, or the fan will be trying to create a vacuum and will not work efficiently.

EDIT. Have a look at the info at the end of this page. It shopws how air flow rate drops over length. Of course, a chicane will slow it even more.

Untitled

 

[JohnW2]

EDIT. Have a look at the info at the end of this page. It shopws how air flow rate drops over length. Of course, a chicane will slow it even more.

I must be dim - the end of which page?

Kind Regards, John

 

[JohnD]

IME you need a fan of at least 240 cu.m/hr when you take steamy showers. You rigid pipe plan is good. Insulating the pipe should minimise condensation but verify that the roof terminal coes not allow rain entry.

The Soler & Palau are very good. The next one up is

4"/100mm In-Line Duct Extractor Fan - 250m3/hr c/w Timer | Soler_&_Palau (5211364500)

But it does cost more.

Beyond that you would need a larger duct.

With a less powerful fan you will need to run it for longer. These S&P are very quiet, especially when mounted on a padded board in the loft.

There are cheaper brands but not as good.

In my bathroom the fan comes on with the light switch, and it is very dry and odour free. You don't need as much power when the shower is not being used, but I don't think you can switch the fan speed on these after installation. With more complexity, I suppose you could have a lower-power fan at the WC position, with backdraught shutters on both. There are fans with a trickle and a boost facility, but I have not seen them suitable for your installation.

 

[Taylortwocities]

I must be dim - the end of which page?

Kind Regards, John

No, it’s me, forgot the link
It’s there now,!

 

[JohnW2]

No, it’s me, forgot the link It’s there now,!

Indeed it is - thanks!

If those figures are correct, I must say that I'm rather surprised that 5 metres of flexible PVC ducting only reduces flow rate by about 35%.

Kind Regards, John

 

[Norfolk Broad]

As there is no window you will need a timer fan (ie runs on after the light goes off). Is the existing a timer fan?
...
Dont forget to provide a way to let enough air into the room, or the fan will be trying to create a vacuum and will not work efficiently.

Thanks for the detailed reply.

Yes, the existing fan has a timer, and I was going to buy one with a timer anyway.
Thanks for the tip from TLC, but another one that caught my eye was this:

Tornado Turbo Tube Professional 4 Inch Inline Extractor Fan with Timer

TT100T PRO Turbo Tube Professional 4 Inch Inline Extractor Fan with timer. Most powerful 100mm mixed flow fan available. See our video review. 24hr Delivery.

www.extractorfanworld.co.uk

What do you think?

Good point on the letting air into the room.
I was meant to say it is a one bedroom flat, so showering with the bathroom door slightly ajar isn't an issue!
We rent it out on AirBnB in the summer to couples or individuals. If it proves to be a problem then I might cut a vent in the door, or plane a bit off the bottom to leave a gap.

I will probably buy four 90° bends, but see if I can get away with just two, and avoid the U-bend if I can.

Thanks again!

 

[Norfolk Broad]

IME you need a fan of at least 240 cu.m/hr when you take steamy showers. You rigid pipe plan is good. Insulating the pipe should minimise condensation but verify that the roof terminal does not allow rain entry.

The Soler & Palau are very good.
There are cheaper brands but not as good.

Thanks for getting back to me.

I like the looks of the Soler & Palau unit - it's like something you'd find under the wing of an airliner!
It's a little pricey, though, and I'm not too concerned about the decibels. The noise for the existing Manrose fan is quite obtrusive, so anything I fit will be quieter.
I quite like the looks of this one, but I'm not sure how truthful the 300 m³/hr claim is:

Tornado Turbo Tube Professional 4 Inch Inline Extractor Fan with Timer

TT100T PRO Turbo Tube Professional 4 Inch Inline Extractor Fan with timer. Most powerful 100mm mixed flow fan available. See our video review. 24hr Delivery.

www.extractorfanworld.co.uk

And you're right about the roof vent and the possibility of rain entry - this is a root cause to one of the problems, and I have to admit I am burying my head in the sand with that one at the moment.
If I ask the landlord to fix it (as it technically counts as the "exterior" of the property), I'm sure there will be a hefty bill to put it right.

Irrespective of whether it is leaking or not, at the moment I just need a better fan and a means to control/capture the condensation!

 

[Taylortwocities]

Thanks for the tip from TLC, but another one that caught my eye was this:

Tornado Turbo Tube Professional 4 Inch Inline Extractor Fan with Timer

TT100T PRO Turbo Tube Professional 4 Inch Inline Extractor Fan with timer. Most powerful 100mm mixed flow fan available. See our video review. 24hr Delivery.

www.extractorfanworld.co.uk

Can't comment on that. I only recommend products that i use and trust.
Mind you, at 300 m³/hr that has got more grunt than the TLC one.

 

[Norfolk Broad]

Hi guys

Thanks for your responses. I've updated my diagram to try and eliminate the U-bend and make the airflow less restrictive.

I've also found that this company do a 110 mm to 100 mm convertor, so it should seat the vertical pipe a lot better.

Soil pipe reducer 110mm to 100mm Inch Reducer

Ventilation Duct Reducer 110mm - 100mm. Use with all standard soil pipe and solid ventilation ducting. Easy fit. Use with duct clamps.

www.extractorfanworld.co.uk

And a backdraught shutter has been added for good measure. I guess the best place to put it is near the fan?

 

[Norfolk Broad]

Can't comment on that. I only recommend products that i use and trust.
Mind you, at 300 m³/hr that has got more grunt than the TLC one.

That's fair enough.

As a matter of interest, going off at a slight tangent...
...do you have any experience with |Single Room Heat Recovery Systems?

I'm not sure if one would be suitable to this application.

 

[JohnD]

I've used one.

It was not successful in a kitchen or bathroom because it did not create suction to prevent steam and odours drifting around the house. An ordinary extractor draws air from the house to replenish the extracted air (usually through the gap under the door) so creates a one-direction airflow from the house, into the room.

Also in my case the incoming air was blown into the room, mixing and preventing stratification (water vapour is lighter than cool dry air so if undisturbed, will rise towards the ceiling and extractor)

 

[Taylortwocities]

Yes, backdraft flap in/ near the fan.
Have a read of thd product information. Looks like they sell an internal one. Not sure if “internal” means “not outdoors”, or internal to the fan…

 

[JohnW2]

... I've updated my diagram .....

Maybe I'm missing something, but I would have thought that condensation could/would arise (to at least some extent) in the horizontal run of duct between fan and the 90° bend. If that happened, that run of duct could presumably 'fill up with water' with the condensation trap fitted where indicated in your diagram?

Kind Regards, John

 

[EFLImpudence]

If fans are so brilliant at removing 'condensation' from a room then why do they not remove it from a duct?

From the description in the OP it appears that the top of the duct is not preventing entry of water and dirt from outside.