Successfully eliminated “P” trap under sink with Hepvo valve

YanniLazarus · September 2020

this is my installation in aT@B320S 2020 model. With the drain on the left of the sink it was hard to get a straight shot to the corner waste line to work. Using a 1 1/2" threaded plastic nipple (black plastic) just below the sink drain kept everything as high as I could get it, and the drain line is as short as possible. Very happy!

Dalehelman · September 2020

You should have been able to connect the Hepvo directly to the bottom of the sink. There by gaining another 3 or 4 inches.

YanniLazarus · September 2020

I couldn't get that to work- my sink drain is closer to the corner than yours, so your horizontal run came low enough on the stack to get the fittings to work. I just dropped mine the 1 1/2 inches for the nipple. My drain location made it harder.

YanniLazarus · September 2020

Hmmm. Plus the fittings. So you are right. Probably around 3 inches lost- but since my drain is closer to the corner, overall not so bad.

Dudlee · September 2020

I was wondering if pulling the sink up and rotating it 180 to get the drain away from the corner would be worth it. The install photo of jkjenn Looks like that’s what the crew did?

Dalehelman · September 2020

Still looks good.

YanniLazarus · September 2020

I think if I were smarter and used other fittings it might have worked a bit better. The slip fittings I used required some minimum tubing lengths. I do think keeping the horizontal run as short as possible is best (and laziness) kept me from exploring rotating the sink.

ReenieG · September 2020

@ReenieG, I agree with regard to the original pic you posted--there is no vent on the sink drain, and that suggests the Hepco valve itself does not require a vent to function properly.

Regardless, the grey tank itself must still be vented to prevent pressure from impeding drainage. I assume in your pic (which is not a T@B) the grey tank is probably vented in another location that is more convenient for the layout of that particular camper.

If you go look at your 320 I'll bet a nickel it looks like the pictures Dalehelman posted with the vent in place.

@ScottG Yes, I have no doubt the pic I took which Dalehelman circled is MY undersink piping.

I guess my "confusion" is that in that pic I posted of my T@B where Dalehelman circled, I don't see a vent. I will have to actually LOOK and see for myself I suppose, lol.

VictoriaP · September 2020

ReenieG said:

@ReenieG, I agree with regard to the original pic you posted--there is no vent on the sink drain, and that suggests the Hepco valve itself does not require a vent to function properly.

Regardless, the grey tank itself must still be vented to prevent pressure from impeding drainage. I assume in your pic (which is not a T@B) the grey tank is probably vented in another location that is more convenient for the layout of that particular camper.

If you go look at your 320 I'll bet a nickel it looks like the pictures Dalehelman posted with the vent in place.

@ScottG Yes, I have no doubt the pic I took which Dalehelman circled is MY undersink piping. I guess my "confusion" is that in that pic I posted of my T@B where Dalehelman circled, I don't see a vent. I will have to actually LOOK and see for myself I suppose, lol.

@reenieG The circled area in that pic IS part of the vent stack, the 90° elbow above where the sink drain attaches to the vertical pipe leads to the horizontal pipe behind the toilet and exits (vents) out the driver’s side of the trailer.

Kr@cken · September 2020

Another newbie question. What would I want to replace my P trap. Is this something that is recommended?

Sharon_is_SAM · September 2020

It is done to free up space under the sink as the “p” hangs down lower and the Hepvo can be mounted parallel to the floor. What kind of trap do you have under your sink in the 2020 Boondock?

Travelin3D · September 2020

I just did this mod in June on my 2020 320 BDL. Here’s a before and after.

GatorEgg · September 2020

Nice. But the ptrap keeps my Keurig kcup secure in there. 😬

TXMacDad · May 2021

Our sink mod in 2014 T@B

Image: https://lh3.googleusercontent.com/QuYnsp9tQ9cSNp2-PSclgh3nJp5grvVbVxUIwWUl8m-oAyZ9tBzQIYyYe3NTvJgCiS6au5VaMZoPuWxKmlrxFCIoPF-CZ5OjMjvW54m_oUhC1v6HgwOH5u3pl-YP3o7Wunt5f8g71wtE0FlNyKoN6OWdn6FsIiV9FmYknsCxXwWP4J2jHlcW4NIHQInCK7GtFjnyAN4_PCSMYNX0ShR6ylZP5-efdfONv-BfAdGrlf_wdva1wiDPOb7nMDGbhKgNgy6E9q61kuQ-15iUvk1VIS2EmNH_zBEbbadCCibvXu8f_027pHuiOJRdhOOFIaShCbvTCcV1rNOQR85OAT6WObuhC0lYsNyAezgH9Juyy5kzGuMXdhzK1nnYX9StI7meTEethc_m1OIRBQY794gkwCL-kibH_VUUjra6DSdkxGBP5wKbgGSqZpjPrrINYuohQzt-dUKGG2AY17hFSSHOPaciyY0yuKQH7T4_vOdIKlPc6nisxjXeoyWnwsFcL88T7WYsM7Fo-5q5_8Zi0MaoJitoLx2sevL7hHGoZHe0_73vzty7dTCov-_T3rhY6OLuKaFdhs9pS0dwbGIhyuCbpujQ1KrnrhAPLJiPshAZzSdCmTMNjYDhtBTtcFSsKZxxsi_WKdiPTiEBzrWLbrTxmDNeUKtcBMVxk0-rgf7DQ_W58_5NZyhjJp0L9a6k2jqs_e_nIbRLtFlQKPhgmv7x0YBA=w582-h839-no?authuser=0

rcarlson1957 · June 2021

Finished mine yesterday.

Denny16 · June 2021

Looking good...

cheers

ReenieG · September 2021

I finally did mine. There was alot of buildup in the p-trap, probably from water evaporation when storing. Just hoping this all doesn't leak! I'm always leery of plumbing fittings when I glue them together, although it's more me than them.

I'm planning on replacing the faucet with a mod I saw from Facebook (link to faucet) and possibly replacing the sink, (link to sink) since it would prob still be doable. (sink is reportedly 1" deeper) Since I used a flex drain fitting I may still be able to mod the sink, although I'm still considering the microwave install under the sink which I think might be sink OR microwave, not both. We'll see after the faucet install.

Image: https://us.v-cdn.net/5021717/uploads/editor/bo/jr7ufblj7e0p.jpg

Image: https://us.v-cdn.net/5021717/uploads/editor/fj/ijc4a40gdamf.jpg

ReenieG · September 2021

@Dalehelman @LittleBoyBlue I like your mod appearances better than mine. Not sure why mine looks slanted in the final pic. Hmmm... It looks like your mod might have been easier to do with those white connections. If mine leaks, I'm copying yours, lol.

GPS_Jon · April 3

I did this one. My first post 2019 320 SBD. The sink didn’t let me route directly to the drain.

Is the black drain pipe securely mounted to the grey tank? Mine isn’t and can be lifted up and down inside lower cabinet.

ScottG · April 3

Good question. My guess--and that's all it is--is that the black drain enters the grey tank through a rubber flange of some sort. This would allow a bit of movement as the trailer gets banged six ways from Sunday rolling down road.

AnOldUR · April 4

@GPS_Jon

Another non-plumber person who used the rubber couplers rather than PVC glue.
I kept the p-trap. Swung it to the back out of the way.

Image: https://us.v-cdn.net/5021717/uploads/editor/8a/da4mldzvb3wx.jpg

GPS_Jon · April 5

AnOldUR said:

@GPS_Jon
Another non-plumber person who used the rubber couplers rather than PVC glue.
I kept the p-trap. Swung it to the back out of the way.

I like your setup. More room without spending money on the waterless trap. I used the Fernco couplers so I could rotate the sweep and not use a T. I might have gone with your approach if I saw it first. Either way, for the extra room in that cabinet it’s worth the modification.

I filled up the sink and pulled the stopper. The sink drained quickly and most of the water went into the grey tank. There was maybe two cups on the ground. My black pvc pipe must not be seated in the tank. I’ll have to pull the shroud and see if I can get eyes on it. The plumbing I added had no leaks.

ScottG · April 6

GPS_Jon said:

...
I filled up the sink and pulled the stopper. The sink drained quickly and most of the water went into the grey tank. There was maybe two cups on the ground. My black pvc pipe must not be seated in the tank. I’ll have to pull the shroud and see if I can get eyes on it. The plumbing I added had no leaks.

In light of this, I retract my earlier guess about the rubber flange. Given the amount of leakage I'd say your drain pipe has parted ways with your grey tank. Please report back what you find and, if applicable, how you fix it.

pthomas745 · April 6

Back in December, @jimcenname installed this "bottle trap" in his trailer. Looks like a simpler install to me, someone with very limited plumbing experience.

https://tab-rv.vanillacommunity.com/discussion/20115/replacing-the-kitchen-hepvo-drain-pipe-with-clear-removable-bottle-p-trap-t-b-400

https://www.amazon.com/dp/B0FG7977MF/?coliid=I18HMIAD81K3ER&colid=3DJSJON9VK2CS&th=1

Looks like this:

Image: https://us.v-cdn.net/5021717/uploads/editor/y9/ipdb87ld66it.jpg

jimcenname · April 6

pthomas745 said:

Back in December, @jimcenname installed this "bottle trap" in his trailer. Looks like a simpler install to me, someone with very limited plumbing experience.
https://tab-rv.vanillacommunity.com/discussion/20115/replacing-the-kitchen-hepvo-drain-pipe-with-clear-removable-bottle-p-trap-t-b-400

https://www.amazon.com/dp/B0FG7977MF/?coliid=I18HMIAD81K3ER&colid=3DJSJON9VK2CS&th=1

Looks like this:

It's still working well for me. No leaking.

GPS_Jon · April 9

The pipe was broken. The threads were still in tank. I had to split the threads to remove that part. Off to the hardware store again. lol
It wasn’t too hard to get it out.

Gomers2 · April 14

Fun fact: The 360 comes with a hepvo type drain (no P trap) in the bathroom sink. Not sure why, since there is a lot of space for a standard setup.

Successfully eliminated “P” trap under sink with Hepvo valve

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