Plumbing rough in

[YotaOnRocks]

Long post, hoping to answer any questions with my initial post.

So I'm finally making progress on my barn and I'm trying to finalize my plumbing plans. I've called a plumber to get a quote but would like to do my plumbing myself to save some money if possible.

I've replaced plenty of failed plumbing components over the years and reworked a few bathrooms but never laid out a new install. My main concern is I will get the venting wrong or use the wrong size drain lines.

Barn is 40x80 with a 20x20 living area inside it. Living area will have a kitchen island with sink and dishwasher, a full bath with toilet,tub,and sink. The barn will have a washing machine and a place to hook up the camper waste line.

Seems pretty simple and easy enough but the fact that I'm putting all the plumbing under the slab has me nervous.

Was planning to do 4" line for rv, main drain line, and toilet, Dish washer and kitchen sink 1.5", tub 1.5", bathroom sink 1.25", and washing machine 2". Does this sound right?

I have no idea where or how to put clean outs in an under slab system.

I have no idea about venting other than it is critical for proper draining. I have found some diagrams showing how to do a kitchen island and I understand how that works but couldn't find much that I found clear about the rest of the venting, as far as size and rules for routing it up (for example can the vent run horizontal and then up so it can be placed near an exterior wall.

My rv drain is the only drain line on the house side of the barn and I prefer not to have a vent pipe through the roof on that side. Do I need a vent for it? If so can I run it over to the other side of the roof peak?

I have attached a drawing I did to scale for our kitchen/ bath layout,1grid block=6" and a layout I did on an app for the whole barn layout to give some visual aid.

The washing machine will be on the wall opposite of the bathroom in the garage area but I didn't include it as the camper is represented as 16' side the whole length to but I have no slide outs on the rear garage section so I actually have another 4' of clearance there.

So am I an idiot and should just pay the man? Or am I an idiot and this is much simpler than I think?

 

[kaiser715]

After the blowout I had while dumping the rv a few weeks ago, I sure wouldn't want to be dumping in the garage. Put your dump station outside. (Unless you are living in the RV, inside the garage)

 

[YotaOnRocks]

After the blowout I had while dumping the rv a few weeks ago, I sure wouldn't want to be dumping in the garage. Put your dump station outside. (Unless you are living in the RV, inside the garage)

I am, we are planning to use the living space to give the kids some room to play with their toys and the kitchen and bath for daily cooking/bathing so life feels a little more normal. We will mainly be using the rv for sleeping and night time toilet trips. Plus side is we will have a nice gathering/entertainment area after the house is constructed.

 

[paradisePWoffrd]

I would do 3" for the washer drain. Some of the new high flow machines require it. Personally, I would not drain the washer into the septic, but I dont believe that will pass code anymore.

For the sinks and tub, I would use 2" in the walls and slab, and drop to 1.5" in the cabinet.

I would likely also put the sink and dishwasher along the wall vs in the island. I have thought about doing a similar build for a while, and I think having access to the plumbing & wiring, in the wall cavity, from the garage side, would be nice.

I have no real plumbing experience, other than fixing the old stuff in my houses, so maybe its all the wrong things.

 

[braxton357]

If you really want to I can help you lay it out, but I work with a plumber and we do several under slabs a year but always quote high because they always suck. You're already off on every one of your pipe sizes, and I'm sure you already know but plumbing and venting an island correctly is also a pain. A good plumber won't use cpvc under slab and if using pex wont have any joints underground. Another question is do you have septic installed already? You'll need to know elevations and distances or you might end up having to install a pump station.

Have a few plumbers quote it, make sure they have a lot of experience with underslab since it isn't common here, then hire one of them.

 

[YotaOnRocks]

If you really want to I can help you lay it out, but I work with a plumber and we do several under slabs a year but always quote high because they always suck. You're already off on every one of your pipe sizes, and I'm sure you already know but plumbing and venting an island correctly is also a pain. A good plumber won't use cpvc under slab and if using pex wont have any joints underground. Another question is do you have septic installed already? You'll need to know elevations and distances or you might end up having to install a pump station.

Have a few plumbers quote it, make sure they have a lot of experience with underslab since it isn't common here, then hire one of them.

I haven't installed the septic yet and it is going on the downhill side so I believe there will be no issue with pipe fall. I would really like to just pay the man, but I'm already way over budget and might try to do it myself depending on the quotes I receive.

Maybe @CasterTroy can recommend a good local plumber.

 

[justjeepin86]

If the cost of me having a repair done at my MIL house is any bearing on what the plumbing would cost, i can't imagine how much it could be. Insanely simple repair work and was drilled for it. Could have done it myself, but was too busy.

Obviously, the design of a new system is much more important.

 

[CasterTroy]

Maybe @CasterTroy can recommend a good local plumber.

Studor vent the island, OR, I can send you the diagram for how to "Chinese vent" it.

RV dump can be as simple as a 4" cleanout between the building and septic tank.

You'd think this would be simple. Plumbing is one of those things that's logical and straight forward, but where you get nailed is inspections. You won't likely bed it the way the inspector wants, and I'll promise you that you will never vert it the way an inspector wants.

Be better to call me. I think you've got my number.

 

[YotaOnRocks]

Studor vent the island, OR, I can send you the diagram for how to "Chinese vent" it.

RV dump can be as simple as a 4" cleanout between the building and septic tank.

You'd think this would be simple. Plumbing is one of those things that's logical and straight forward, but where you get nailed is inspections. You won't likely bed it the way the inspector wants, and I'll promise you that you will never vert it the way an inspector wants.

Be better to call me. I think you've got my number.

I'll give you a call tomorrow. I don't require any inspections on this building so I don't have to please an inspector..... but that also means nobody that knows better will be checking behind me.

 

[Loganwayne]

I'll give you a call tomorrow. I don't require any inspections on this building so I don't have to please an inspector..... but that also means nobody that knows better will be checking behind me.

No inspector I'm assuming you told them it's an ag building for an exemption? Pretty sure plumbing voids that exemption. I would just double check. Because when you go to build your house that will need to permitted and they see a structure with plumbing and electric they will put a stop order on your house and make the house process complete hell.

 

[rockcity]

It’s not hard. Biggest thing is knowing sizes of piping and know when to use a combo wye (or wye with a 1/8) versus a sanitary tee.

That being said, I pay the man to do plumbing because everything is inspected that I do. But if it wasn’t, I’d probably do it myself.

 

[YotaOnRocks]

No inspector I'm assuming you told them it's an ag building for an exemption? Pretty sure plumbing voids that exemption. I would just double check. Because when you go to build your house that will need to permitted and they see a structure with plumbing and electric they will put a stop order on your house and make the house process complete hell.

They know it will have electricity and water run to it and do not require any inspections on them, but I did not pull a septic permit because I thought it a waste of $500. The inspector came out to sign off on my well permit and leaned on the pallet of infiltrator chambers while we talked, and never said a word. Rockingham county is pretty relaxed, thank you for the concern and warning.

 

[rockcity]

They know it will have electricity and water run to it and do not require any inspections on them, but I did not pull a septic permit because I thought it a waste of $500. The inspector came out to sign off on my well permit and leaned on the pallet of infiltrator chambers while we talked, and never said a word. Rockingham county is pretty relaxed, thank you for the concern and warning.

Just make sure you keep the septic far enough away from your well and preferably downstream.

 

[cranbiz]

They know it will have electricity and water run to it and do not require any inspections on them, but I did not pull a septic permit because I thought it a waste of $500. The inspector came out to sign off on my well permit and leaned on the pallet of infiltrator chambers while we talked, and never said a word. Rockingham county is pretty relaxed, thank you for the concern and warning.

Rockingham County isn't all that relaxed. A lot depends on the inspector. Mike is good and easy to deal with, some of the others, not so much.

 

[CasterTroy]

First, I'd made the building 3-4ft wider to place a floor mounted Jan type sink on the right hand most wall on the other side of the RV so there will be a fixture to wash past the cleanout I've shown directly under the right side of the RV. This way when you dump you can just run the water in the Jan sink and wash all those turds down the line. This also gives you an opportunity for a door in the back corner for egress in case something were to happen (fire) between the camper and the garage door. The red line would be the sewer. Direction would be to the left, origination at the Jan sink next to the camper.

Here is a sketch of the way that I would pipe the building. Water coming in the same way the sewer does, below slab, and rising up in the kitchen sink island with shutoff valves. (also need a shutoff in a box just outside. I would recommend also putting a spigot in that box to drain the building for winterizing JIC)

Here is a sketch of the entire building

Closeup of the kitchen sink

Another view of JUST the sewer piping. (green is vent)

I would rise up out of the slab in the wall to feed the bathroom above ceiling, then drop back down below slab for the water heater and Jan sink. NO JOINTS BELOW SLAB!!!

Piping at Jan sink and water heater (mounted high on wall above Jan sink)

I would depress the cleanout for the RV 2" and slope the slab to the top of the threaded cleanout in a 2ft square if it were me...just to have a small containment area if things went sideways.

It's not labeled but 4" up to a 3" wall cleanout, then 2" vent. You can tie this vent into the toilet vent if there's room in the trusses and only have one vent thru the roof if you desire.