Hi everyone, my girlfriends brother is planning on converting his garage into a bedroom with an en suite bathroom.

I've recently completed an intensive plumbing course and have my city & guilds level 2. However I haven't secured work with a plumber yet and I do not have the experience to take on this job myself.

Could anyone offer advice on what's involved? Do I run the pipes from the house underground to the garage and where do I cut into the supply? Do I need a macerator pump in the garage to take the waste to the stack? What's the best choice of shower?

Thanks guys, I apologise for my ignorance!

Gadgie...

Lots of details to consider here...

1) Water heating source. Is it enough for an additional bathroom?

Are you planning on additional water heating source in the garage?

Are you on pump or town/city water?

2) To determine need for a macerator pump you need to determine if you can run a 4" pipe from the main drain line in the house or from outside the house to the garage with proper pitch (here in USA it is generally 1/8" per foot for 4" pipe and larger, and 1/4" per foot for pipe 3" and smaller.

So measure out total distance from main drain to gargage..remembering that you need to cover the pipe with at least 12" of dirt at highest point outside and at least 2 or 3 inches of dirt PLUS concrete pour inside the building.

3) I don't know where freeze line is in your area... but that will certainly be a concern for the WATER MAIN LINE into the building. You will need to run the water piping BELOW the freeze line to prevent any freezing in future.

4) You cannot usually run the WATER line in the same trench as the WASTE line... or at least they must be a certain distance away from each other.

You need to call local codes enforcement in your area regarding #2 and #3 and #4 as each town/county/state/ and even country and CONTINENT seem to want to do things their own way!!

5) You would cut into the water line nearest to meter or to pump... or nearest the largest water pipe in the house (usually at the meter or pump). I would not send anything smaller than 3/4" copper tubing to the garage, and in USA it needs to be type K copper tubing or thermoplastic pipe (1" minimum if possible).

6) You would cut into the sewer at the place that makes the most sense... that may be inside the house.. or it may be outside the house. Depends on if you can or want to drain the bathroom by GRAVITY or by PUMP.

Let me know what you can here... will see what else we can do.

MARK

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Let me add a bit to Marks answer. Most bathroom groups are roughed in like this.
Toilet connects to sewer main . Lavatory connects to toilet drain and runs a vent off the top the stubout tee out the roof. The toilet wet vents through the lavatory vent and the tub/shower connects to the lavatory drain and is wet vented by it. This is a normal rough in and is acceptable both by local and state codes and also The Standard Plumbing Code Book in 90 percent of the country. Check your local codes.to make sure you're not in the excluded 10 percent. Good luck, Tom

Thanks for replying guys. I've had a good look at the job tonight and this is what I think I'm going with (but let me know if it's not going to work!).

I'll be installing a shower, sink and toilet in the garage. The kitchen sink is opposite the garage, so I'm thinking I'll cut into the cold mains water pipe before the tap and T it off to outside the house. Then run it underground at the required depth to the garage, bring it inside and pipe up the appliances.

I'm thinking of using an instantaneous electric shower and a point of use under sink heater to provide the required hot water. With this set up I should only need the cold mains coming in which would be easiest for myself to install. All heating will be provided by electric heaters.

It's not possible to run the waste pipe at the correct fall into the soil stack. I'm looking at getting a 3 input macerator pump to tie everything into. Am I right in thinking I can hook all the waste into this unit then run it underground to the soil stack, without having to worry about having the correct pitch into the stack? i.e. can I just run a pipe in any old fashion from the macerator into the soil stack?

Hopefully this set up will work! Please, please let me know if this is not going to work or is just a stupid way of doing things!

By the way, I live in Scotland so some things may be slightly different. Also, this installation is not intended to be permanent. He's looking for the cheapest way to install a bathroom and bedroom in his garage so he can rent out his bedroom for a while.

Thanks for your help.

Will this fill the bill? (See image)

Hi Gadgie:

I knew you were UK as soon as you said... en suite... ;) I'm a Gordon with long family history and one KICK A** coat of arms back in Scotland!

Considering all you present everything seemed fine... EXCEPT the drainage and water supply to garage!

The waste line still needs to pitch back underground toward the main drain at the house or again... outside the house... that make sense? PUMP OR NO PUMP!

If nothing else, you may need to drain the garage by gravity to a macerator pump INSIDE THE HOUSE BASEMENT... not inside the garage!

Effluent sewage ejector may work better here!

Check out Zoeller Corporation for information on both macerator and effluent sewage ejector pumps.

Again, would have to drain garage full size 3" or 4" to pump at house for these to work... so recommending the effluent ejector back at the house.

Also note that the kitchen sink water pipe may not be large enough to feed both the kitchen sink and the ENTIRE piping for cold and instant hots all at the same time. Look for 3/4" tubing size as minimum to garage...not 1/2".

Imagine 1/2 way into shower and someone in the house opens the kitchen sink while someone is taking a shower at the garage.. all supplied by one 1/2" pipe..? Could get ugly!

Let us know what you think.

Best choice of shower... my opinion will be to go with a pre-molded shower floor such as made by swanstone and then use concrete board and tile to finish the walls!

Shower floor is set into a bedding substrate to keep floor from creaking, etc.

Swanstone

Mark's bang on when he recommends uping the supply to 3/4".
You state,

Quote:

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It's not possible to run the waste pipe at the correct fall into the soil stack.

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Why not? You're satarting at the frost line and running to a basement stack vent. Seems to me there's plenty of fall there. How much of a run are we talking about? What is the reason that you can't install a regular rough in, drain it by gravity to the basement? Why the added expense of a sewage pump or grinder? Let us know. Tom