Loud Foghorn From Plumbing Parts




About: Woodsman and field tutor on a week day. Life long inventor, designer, engineer for the rest of the time. From items that make life easier to items with no reason to be....other than the idea popped into my h...

This is a how to for building a loud foghorn from easy to get plumbing fittings and an inexpensive double acting air pump, the idea was to emulate the hand operated type used on small ships until the 1950's shown in pic 2.

Step 1: What You Need

Here are the basic parts to make a noise

A hand operated pump, a sink waste trap and a rubber glove (for the diaphragm)

Step 2: Preparing Parts

The trap needs the down tube cutting off 1mm above the level of the outer edge, this cut needs to be accurate as this is where the diapragm will go so make sure you smoothe the cut edge with emery cloth.
 I cut the bowl down to size by cutting a section out and sticking the 2 end parts back together. drill a small hole in the back of this part so that it isn't fully sealed.

Step 3: The Noise Maker

Cut a circle of rubber from the glove that is just bigger than the size of the o'ring that seals the bowl, lay it on to the o'ring joint  face and trap it with the o'ring before winding on the bowl.

At this stage if you blow into the side of the fitting you will make a noise :)

Step 4: Attaching to the Pump

I am fortunate as I have a lathe and turned up the adaptor from a piece of plastic, but an adaptor can be made from standard plumbing plastic fittings glued together, the main thing to remember is to have a short length of the connection tube that comes with ther pump glued into one end to allow the adaptor to be screwed on and off (allowing the pump to be used for its original purpose).

Step 5: It Should Now Work

With the parts assembled you now have a working horn and could leave it right there......

Step 6: Making It Lower and Louder

This where you can go mad!  Get as many plumbing parts as you can screw and glue together to make the sound path long and wider.
I added a second sink trap........

Step 7: Making It Even Lower and Louder

... I also added a shower trap......
The second picture shows an adaptor for attaching the 100mm diameter soil pipe adaptor shown stuck on the top in the third picture. This is where the last part will plug in!

Step 8: Making It Even Lower and Even Louder

... the last part being a toilet pan connector! the rubber boot at the bottom plugs into the adaptor, the seal at the top end was removed.

Step 9: Assembly of Horn Parts

The plumbing parts were all screwed together in as small a space as possible and connected up.
An MDF base was cut to support the lower end using a nut and bolt through the cap of the shower trap, this makes sure it is pretty sturdy.

Step 10: It Sounds Like This.....

Ignore the bumble bee that flew past as I was recording and imagine this a lot louder:)


(I tried to imbed this using the code from vimeo but it came up as error on page so I gave up:)

I hope to hear the call of the fog horn throughout the world once you all build your own!

Regards rog8811



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    26 Discussions

    I've never seen anybody attempt this from plumbing parts! Could be a fun DIY project for the kids!


    5 years ago on Introduction

    I have seen several items built out of recycled plumbing parts but this is something new to me. I did not know that you could actually build a sound instrument that actually works fine out of plumbing fittings. I am still unable to figure out how air from the pump can actually produce sound just by passing through the pipings. I guess I would have to build one up to experience it personally.

    1 reply

    Reply 5 years ago on Introduction

    The sound is made when the air from the pump forces its way past the rubber glove diaphragm the pipes just shape and amplify the sound.
    Good luck with building your own.

    Regards rog


    6 years ago on Introduction

    Dear rog 8811,

    I love your project and will start to build one soon. Just so I get my mind around what you are suggesting - the larger the diameter (of the horn section) the deeper the noise? If this is the case have you any comment on the max size that is achievable?

    I was thinking of using an old fire extinguisher and cutting the bottom off.....

    Thanks in advance

    1 reply

    Reply 6 years ago on Introduction

    Hi Chief, from experiments when building mine every time I lengthened the air path, by adding bits in, the pitch went lower.
    The bigger the horn outlet the louder it became.

    I hope that helps you with the design, good luck!

    Regards rog8811


    6 years ago on Introduction

    Hey Rog, Great project! I want to make one, but where can I find a bottle trap like the one you used?

    1 reply

    Reply 6 years ago on Introduction

    Hi, I am UK based and found the trap in either a B&Q or Wickes store, sorry I cannot give you any more than that.
    Good luck with finding the correct part.


    7 years ago on Step 2

    You could use pvc solvent adhesive, the sort used when joining plastic pipes.
    I think I used quick setting 2 part epoxy...5 minute araldite.


    7 years ago on Step 2

    How do you "stick" the 2 end parts back together?


    7 years ago on Step 10

    This horn could be used to accompany the barking dog from next door. Or better still, use it when the barking dog's owner is trying to get some sleep. I like this one, and with a bit of echo added to the sound, we could be out on the calm icy seas off of Newfoundland.

    1 reply

    Reply 7 years ago on Introduction

    I mounted a motor in the end of the horn to rotate a baffle, a sort of leslie speaker cabinet type thing, it spun up a baffle to try for a reverb... I didn't have time to get it working as I was a day away from halloween and didn't have the time to play.....

    I must try it again with a higher geared motor some time.

    I am pleased that folk like this build.

    Regards Rog8811


    7 years ago on Introduction

    Get some aluminum flashing, roll it into a cone shape, use aluminum hvac tape to retain the shape and then use the tape to secure it to the foghorn. By building four or five of these things with differing megaphone sizes your neighbors will quake with fear, as they think that they are hearing the aliens from War of the Worlds. How fun would it be to build about 20, and then set the neighborhood kids loose with them?

    I think of Robert Duvall in Apocalypse Now, "I love the smell of napalm in the morning,..., it smells like victory!"

    I say, "I love the sound of foghorns in the morning,...,it sounds like aliens have emerged from underground!"

    I'm not following where we need to "drill a small hole in the back of this part so that it isn't fully sealed." Can you clarify this with another diagram or more information?

    Also, is it necessary to "cut the bowl down to size by cutting a section out and sticking the 2 end parts back together?" Does this effect the sound if you don't?

    2 replies

    Reply 7 years ago on Introduction

    The hole is just a small one drilled somewhere in the screw on domed cover  to make sure that the volume behind the diapragm isn't sealed. The same part in fact that you asked about cutting.......
    I do not know what difference not cutting this same part down in length will make, try it!
    I shortened it as most fog horns have a very small volume of air space behind the diapragm.

    Hope that helps.

    Regards rog8811


    Reply 8 years ago on Introduction

    I did look at a traffic cone when I was gathering parts, the trouble with them I found was that they are very heavy and actually damp the sound a bit due to the thick wall. I doubt I will paint it as I like the fact it looks like what it is, a load of plumbing fittings connected to a pump :)