Ideas for hybrid dosing septic system?

[viper1]

I am putting together a design for my own system. I have some options but the over all goal here simplicity and some form of dosing to the field instead of a trickle.

I am sure some here understand how bad a standard gravity system with 4" perf can work regarding aeration, rest time, bacteria, etc. Dosing is just much better but they you get into another tank, a pump, floats, alarms, yada, yada.

My system will require a 1500gal tank and around 500ft of lateral. I am looking to keep the 4" perf like a gravity system, then consider maybe a "passive dosing" system where the field can be flooded somehow in a hurry. As we know, dosing really does not need much pressure and 4" pipe offers massive volume and big holes. I realize it would not work "quite" as good as a standard dose system, but I am looking for redundancy so if there is any concern or issue, I can easily flip it back to gravity as a temporary.

I was trying to come up with a way I could sneak in a 3rd chamber in the 1500gal tank which could provide "micro doses". I would love to do this with siphon action but I might be stuck with a pump. The biggest thing here is only 1 tank.

I would bet that if you flood the field quick enough, even the big 4" perf would load up and spread the love around, but most important, allow a rest period.

 

[Atomic1]

Personally, I think you'd be better off sticking with standard gravity system and focusing on the details/design of your field rather than monkeying around with a specialized dosed system. I would consider oversizing the field and incorporating a simple a control valve to alternate rest periods between certain laterals throughout the year. Your stated lateral lengths mean nothing unless you provide your expected daily flow.

It is also important to consider the details at your d-box. I have seen poorly detailed boxes send too much flow to a certain lateral, which causes a cascade failure of laterals across the field. Limit flow velocity to the box!

If your jursidiction allows, consider dumping greywater into a seepage pit instead of the septic system.

 

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[Smooky]

Atomic 1 made some good points. If a pump is not required I would avoid installing one. To properly size the system the expected flow rate/design flow rate is important. What is the septic system going to be used for? Is it a home? Also what restrictions does the site have? Is it sandy or a lot of clay? Do you have a high water table. Is soil depth a problem etc? Has the soil absorption rate been determined for your site? It is tricky adjusting the flow in a distribution box (D-Box). Another option is to use a pressure manifold where it is easier to get a more balanced flow.
A Bull Run Valve as Atomic1 suggest to switch fields to allow a resting period is probably a better idea than a bell siphon system. Siphons can clog up and cause problems.

 

[viper1]

Appreciate the responses. I am a little surprised with the "do only what is required" response. There is a couple reasons I insist on a pressured lateral field. For one, gravity feed systems trickle to the field and do not distribute effluent to the entire field thus creating a much shorter life before biomat becomes an issue.

Second, because there is a geothermal tubing field under the septic laterals, a fully wetted field will increase the efficiency and is worth the investment.

I did however realize that I cannot make a passive siphon system work due to an issue with head pressures. I just don't have enough head to make it all work, and I will have to install an electric pump. However, I had a good talk with one of our precast locals and we came up with a solid says to make this all work out well.

Now, I realize a gravity system might work out for many, many years, but I don't plan on moving in the next 40yrs and I am trying to keep this system functioning as long as I am around. I have been around gravity systems that failed and almost ALL of it could have been prevented.

 

[Atomic1]

I own a septic system and have inspected many. I dont see how adding capacity to your laterals and a valve is "do only what is required". My point is that adding non-standard complexity to the tank end of the system without much thought of the absorption field can end up backfiring on you. I suggest buying the book The septic system Owners Manual by Lloyd Kahn; chapter 9 has a bit on the setup you're describing.

 

[viper1]

Because I have determined I will have to add a pump to run a dosing system, I will revert back to standard pressure pipe for the laterals. The minimums per county inspector is 1000gal 2 chamber tank, and 200ft of lateral. I am going with a 1500gal tank and 500ft of lateral. They do not require dosing, but I am adding that.

I have honestly not built a dosing system but certainly have built several gravity systems and lived on a septic. I don't like the idea of a pump but I don't really have a choice if I want a dosing system.

Biomat is a real concern with gravity systems.

 

[Atomic1]

I would be concerned about introducing a pump into your primary tank as this will cause the level to rise and fall significantly, thereby stirring up solids and introducing them into the leach field. All of the dosing systems I've encountered utilize a separate pump tank for this reason.