Suggestions for dump & pump for RV garage

CaptBill · 03-28-2010, 08:26 AM

I am looking for some ideas on how to provide for a "dump station" near the garage I am building. Presently, I have an RV pad beside the house, and there is a dump station right behind it. I'm building a new RV garage about 100' from there, and the garage sits at an elevation 4 ft or so, lower.

I have the trench still open, for the conduit for wiring to the garage, and am thinking of putting some sort of plumbing pipe, maybe 1" (?) in there too, for a macerator pumpout at the garage.

Please don't tell me I shouldn't have built the garage on property lower than the house and septic. There was no other choice, as the yard slopes away from the house, on sides and rear.

Have any of you done this, or have any suggestions for me? I know the saying, but can I pump uphill?

RVThere · 03-28-2010, 08:50 AM

You may want to consider laying a 3-4" rigid PVC pipe and then a 1" flex pipe inside the rigid. That way if you do get a clog, you can just pull out the flex, clean out the clog, and push (or pull if you have access from the other side) it back through. I will also give you a raceway for any wires, fiber optics, or future enhancements. I would definitely place a riser on each side so you have easy access to the terminal connections.

PlayItForwrd · 03-28-2010, 09:42 AM

You need a "sewage ejection" system--pump to the system with the macerator, let the system do the rest--

Here's a link to one:
Sewage packages - installation instructions - Zoeller Powerflush toilet systems Quick Johns from famous Plumbing Supply

**Gary RVRoamer** · 03-28-2010, 09:54 AM

A good macerator pump system like the Sanicon can pump uphill to a height of 20 feet using 1" pipe, so adding a pipe to your trench makes sense. I go larger, though, at least 1.5" pipe. It doesn't cost much more and reduces back pressure considerably.

I like the idea of laying a bigger pipe (or an additional one) for a cable raceway as well. Wished I had done that several times!

CaptBill · 03-28-2010, 06:20 PM

Thanks for the suggestions. Since there will be back-flow, e.g., I'm pumping uphill, I'll need to provide for some way to let the pipe drain to something like a dry-well; a hole filled with stone & sand. So I would like to select a pipe size that is a good compromise; no too large as to have a lot of volume that flows back. And I'll need some sort of diverter valve, so I can direct that backflow to the designated drywell.

Maybe 1" or 1.25" would be about right.

I've done electrical wiring/wire fishing for a living, so I'm already with you on running extra wire chase conduits. In fact, I am installing phone, 2 cat5e, and video cables, and will have a pull string, all in conduit large enough for uprades. All conduit runs are smooth, sweep turns for easy pulls.

Any other ideas on the pumpout that might help, please post. I will be closing the trench probably by Wednesday. weather permitting. Thanks to all.

Rex · 03-28-2010, 07:55 PM

Rather than a dry-well to drain the pipe after pumping, why not a cut-off valve so there is no need to drain it. If you do drain it, you will want to make absolutely sure you have clean water all the way through the pipe before allowing it to drain, unless you can deal with the resulting smell if the water is not clean.

Just don't forget to open the valve before turning on the macerator.

exrench · 03-29-2010, 09:27 AM

Be cautious about dumping forty gallons of black into your septic tank unless it is designed for such operation.It probably has never received such a large amount since it was installed and you might very well destroy your leaching field if enough sediment reaches it.Most residential systems benefit from slow input.

**Gary RVRoamer** · 03-29-2010, 09:35 AM

If you have plenty of fresh water available, just flush the tank until you are pumping more or less clear water up the pipe. Then close a shutoff valve on the pipe and leave it full of water.

An 1.25" pipe is 50% greater capacity than a 1", so that reduces back pressure a lot, at the cost of some volume. 1" is probably ok, though.

CaptBill · 03-29-2010, 02:53 PM

Rex, I suppose it would be ok to leave water in the pipe, with the exception of during winter. The pipe would be subject to freeze, at the point where it comes up out of the ground. I could always open the valve once a season, to let it backflow. That's a detail I have to think more about.

exrench, I am not saying the septix was designed for this, but it is a 1000 gal tank serving only 2 people in the house. We have had the existing dumpstation hookup for at least 5 years, and have had no problem, so I wouldn't expect that to change.

Gary, I'm leaning toward the 1" ID. How many gallons would a 1.25" pipe, 100' long, contain? The run is about 90', but there will be 2 elbows of 45*, so added friction for that. The lift is approx 4.5' to 5' to where it would enter the 4" sewer line to the septic tank.

Rained all day today, so didn't get any work done. In fact, I have some new trenching to do now that it has filled up considerably, from the sides of the trench collapsing. :(

**Gary RVRoamer** · 03-30-2010, 07:48 AM

To find the volume of a pipe, multiply the cross sectional area (pi*radius squared) in inches x length (in inches) to get cubic inches. 1 cubic inch = 0.0043 US gallons

A 1" pipe may not be exactly 1" I.D., but it's probably close enough for your purposes.

A 1" pipe has a radius of 0.5, so a 10 foot length is
3.14 x 0.5 x 0.5 x 120 = 94.2 cubic inches
94.2 x 0.0043 = 0.4 gallons.

Thus a hundred feet of 1" pipe holds about 4 gallons.

A 1.25" pipe x 10 feet is about 147 cubic inches or a bit over 50% more.

CaptBill · 03-30-2010, 02:03 PM

Thanks for the info Gary. May go with the 1.25" line after all.

CaptBill · 04-02-2010, 09:02 AM

I want to come back to the forum for your take, on 1" VS 1.25". I bought the larger size and am about ready to do this, when I called one of the macerator pump manuf. (Johnson pumps). Since the pump discharge is 1", I wondered if the 1.25" pipe would be ideal for a 100' run, or comething else.

The tech said that increasing the pipe size would increase the backflow pressure on the pump, reducing the flow. I was a little surprised by this, and he said let's take an extreme example. amd cpnnect the pump to a 5" pipe, with a 5 foot rise. The back pressure on the pump would be even higher.

I pointed out the a larger pipe would have less resistance to flow, and he said "I guess that's true, so you could use the larger dia. if that works." That made me think he isn't sure about the effects of length, diameter and lift.

Can anyone shed some light on this?

JohnFitz · 04-02-2010, 10:23 AM

You're on the right track and the tech is mistaken about pressure increasing with diameter. I'd say you bought the right diameter pipe. By increasing to the next size (1-1/4") you are assuring you wont get any clogs in the pipe - something that's far more important than how ideal the flow rate is.

**Route 66** · 04-02-2010, 11:30 AM

Quote:

The tech said that increasing the pipe size would increase the backflow pressure on the pump, reducing the flow. I was a little surprised by this, and he said let's take an extreme example. amd cpnnect the pump to a 5" pipe, with a 5 foot rise. The back pressure on the pump would be even higher.

I believe what he was saying was the weight of the water in a 5" pipe being pumped uphill would be more than the pump could handle.

We need our resident engineers to comment.