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House is 30 years old, and I assume the septic system is as well. Septic has been supposedly pumped twice a year. What kind of questions should I be asking about it? I've never had a home with a septic system before.

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    Any questions you ask would probably require the expertise of an inspection specialist to answer. All the owner will be able to say (or want to say) is "it's working great now". I'd spring for an actual septic company to have a look.
    – isherwood
    Commented Jun 12 at 20:28
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    Can you expand on what makes it mechanical? Is there a macerator/auger in there - a literal shit-stirrer ?
    – Criggie
    Commented Jun 14 at 0:51

9 Answers 9

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For any home purchase, I would ask these questions:

  • where is(are) the tank(s)? How many? How big are they?
  • where is the leach/drain field?
  • is there a pump (air, effluent, sewage)? is there an aerator?

And specific to your purchase:

  • Why was it being pumped so frequently?
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I've converted isherwood's comment into an answer, with the additional backing that I was employed by a local company for a period of many years.

If you want peace of mind, consider to contact the septic company used to perform the pumping. Companies in my area are required to provide an inspection when doing service on a septic system.

One may be concerned if the drain field becomes saturated, or if the drain field component pipes are crushed or otherwise damaged. The drain field pipes are nearer to the surface which allows the effluent to interact with atmospheric oxygen. Backups can be created if the system is damaged.

If you are unable to determine the vendor/contractor, contacting a company of your choice for a pump-out and inspection will provide that peace of mind. Twice a year seems rather frequent, unless a warranty contract required this. One of the local companies warrants the septic system they service, but only if a pump-out is performed annually.

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As an owner of a home with a septic system for over 30 years, I would be wary if I was told the system was pumped twice a year.

That said, this can depend on where the home is located. I'm in Florida. Here a well maintained septic needs to be pumped about every 3 to 5 years. Systems that were pumped often were an indication of misuse and possible blocked drain fields. Your location may be different.

If you are financing the home the lender may require an inspection. FHA and Va loans required inspections and now many lenders are adding that requirement in Florida.

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    I'd agree (as a fellow septic system owner), that if it's being pumped every 6 months, then it's either seriously undersized for the number of inhabitants, they're clueless on how often it needs to be pumped, or there's some sort of drain field issue. My guess is the last, especially after 30 years. For reference, I'm in Iowa, and we typically pump ours every 4 years, and even then our service person has said it wasn't full of material yet.
    – Milwrdfan
    Commented Jun 13 at 0:33
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    It could be that they have a tight tank. Those require frequent pumping.
    – Cheery
    Commented Jun 13 at 16:41
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    What is a "tight tank"? I have never heard of that.
    – RMDman
    Commented Jun 13 at 16:42
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    If the house is near a lake or does not have the yard to fit a drain field, in some places they allow you to install an underground storage tank with no drainfield. So it has to be pumped every time it fills up with liquid. Those underground tanks are called "tight tanks"
    – Cheery
    Commented Jun 13 at 16:44
  • Thanks for the explanation. They are not used in my area. In that situation the system would be mounded.
    – RMDman
    Commented Jun 13 at 16:46
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The main components of modern septic system include the connection to the house, the actual septic tank, a D-box, and the drainfield. There is not much you can inspect yourself, and there are inspection services just for septic tanks, and in my opinion, they are really worth the money. In some areas, pumping companies do inspections as part of routine pumping, in other areas, it's the installation/excavation company that does inspections, and the inspection can only be done in the presence of a town/city official from the sanitation/health department. You have to ask.

Ask the current owner for the as-built plans for the septic. I don't think you can get a CO (certificate of occupancy) without those drawings, so they must exist somewhere.

If you call for an inspection and the system does not pass inspection, you can get a discount on the price of the house, to cover the costs. Once you discover the issues, the owner will have no alternative but to give you the discount: either they give you the discount or delist the house while they pay a contractor to install a new one.

Note that in many jurisdictions, you cannot sell a house without a passing septic inspection, and the seller pays for it. Ask your agent and lawyer about how things work in your area.

About the frequent pumping: it is possible that the system is undersized for the house, but this is unlikely. Septic systems are rated according to the number of bedrooms in the house, not the number of occupants. So if your house was a 3-bedroom but had 7 people living in it, it's possible that the system was working above capacity. But again, this is rare.

However, if the house is near a lake or has a yard too small to accommodate a drainfield, it's possible that you have a tight tank. That's a tank without a drainfield, and they do fill up quickly and they do require constant pumping. A house with a tight tank is worth less than a house with a normal system, so be sure to check.

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There are two kinds of septic inspection. In one, dye is put in the system so they can track flow and measure things. This is the kind of inspection that would be performed by a home inspector and can be purchased as an add-on service when the house itself is inspected. In some jurisdictions, a septic specialist might be required instead of a generalist home inspector.

In the other, they pump out the system and visually inspect it. This kind of inspection is performed by a septic maintenance company. If the system is being pumped out semi-annually, that company presumably did that. You could talk to them. The caveat being that they are employed by the seller. Hiring your own would get a more independent answer but cost more (often you can talk for free). The leading question is why the system needs pumped twice a year. If the current company gives you a bad answer, you can stop trying to buy the property. If a good answer, follow up with an independent inspection to verify it.

You can get both kinds of inspection done if the results of one worries you or if you just want to check.

Links found via Google, no affiliation.

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You need an expert (or two) to inspect and advise you. Twice a year is not a normal case for a septic system, so you need someone who knows what they are doing to tell you what's wrong and how much it will cost to make it right.

With the assumption that the septic system is 30 years old, I would approach the transaction assuming that it needs to be replaced and move to adjust the price accordingly, backed up by a quote from a company ready to do it.

Anything short of that I would want to have a price for, as well. Having professional opinions and quotes is important leverage for your negotiating.

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Something to check into besides what is mentioned in the other answers is to find out what is allowed if you have to replace the leach field or tank, because there may be new laws put in place since the existing system was installed. It's possible for example that you would have to install an aerobic system which could cost more as well as having pumps that have to be maintained, or there could be restrictions on where a new leach field can be located. In some cases you may not even be allowed to install a new leach field, and will have to install an aerobic system combined with above ground sprinklers. Even if the inspection passes you still might want to have this information in case the system needs replacing within the next five or ten years, because while the old septic system will probably be grandfathered in, a replacement system would have to meet the new regulations.

This information would also apply if the inspection fails and the seller is giving you a discount, as you would want to make sure that they give you enough to cover a new system that meets current regulations. So you will want to get not just a pass/fail inspection but also an inspection specifically related to replacement, i.e. what type of replacement system and size would be required. You can then shop that inspection with some local septic companies and get some quotes. If the current system passes the seller may not be willing to pay for a replacement type of inspection, if that's the case it would probably be worth paying yourself to have it done.

In case anyone is interested in what an aerobic system entails, I have some experience with this when my mother's thirty year old septic field needed replacing three years ago, and below is a detailed account of the replacement.

Her septic system was still functioning but it no longer handled having a full house of visitors very well due to the increased number of showers, dish washing, and toilet flushing.

She lives in an unincorporated area in a county in Texas that is otherwise not as strict as other counties. For example she can burn trash if she wants to, although she doesn't. She looked into having a new leach field installed using the existing tank. However the inspector told her that based on the newer regulations he would not be able to approve a new leach field because her soil failed based on the following criteria: Soil Class, Soil Texture, Soil Structure, and Depth of Restrictive Horizon. As for that last one, a definition that I found from North Carolina which presumably is similar is:

Restrictive horizon means a soil horizon that is capable of perching ground water or sewage effluent and that is brittle and strongly compacted or strongly cemented with iron, aluminum, silica, organic matter, or other compounds.

The inspection gave a detailed list of what would be required for a replacement system, which in her case had to be an aerobic system which used sprinklers, i.e there would be no leach field. This required a new tank with three chambers, each chamber is generally referred to as a "tank" even though in her case it was a single 1,500 gallon tank made up of three 500 gallon chambers.

The first tank is the "trash tank" (pre-treatment tank) where all liquids and solids go . Similar to standard systems this is where most of the solids wind up settling, and where bacteria begins to break down the waste. Liquid in the first tank then overflows into the second tank, similar to other systems, for further settling of solids and bacterial breakdown.

The difference with an aerobic system is that there is an air pump that pumps air into the second tank, sort of like in a fish aquarium. The pump is located at the back of her house connected to electricity, with plastic tubing running underground to the tank. In my mother's case it is a 1/2 hp pump at 40 psi. The air pump runs pretty much constantly, and this greatly accelerates the bacterial breakdown. Whereas a typical septic system reduces organic material by about 30 to 40% in the septic tank, leaving the leach field to do 60% to 70% of the work, in an aerobic system the tank does 90% of the work and the leach field only has to do 10% (source Aero-Stream). The air pump has a filter that has to be inspected and replaced per a schedule. And of course a failed pump has to be replaced.

The next big difference with my mother's system is that instead of the second chamber overflowing to a leach field, the overflow from the second chamber goes to a third chamber, where chlorine bleach is mixed in. My mother has to pour one gallon of bleach into the top of the tank every month.

Now the fun starts, so to speak. Another pump, this one located inside the third chamber, pumps the disinfected overflow water from the third chamber through irrigation pipes to sprinklers. This pump runs on a timer, also located at the back of her house, which is scheduled to run at 2:00 am. Normally that is sufficient, but when she has a lot of people visiting then it will run whenever the third tank gets full, whatever time of day that might happen to be. They are rotating sprinklers that don't really spray so much as shoot a stream of water about fifteen feet. The water is safe for lawns and pets but not for drinking (as if anyone would want to).

The size of her system dictated having three sprinklers, and she hoped to have them installed in her mostly unused backyard. However her water well is located back there and the sprinklers have to be 100 feet from a well. This would have placed the sprinklers far out into her hay pasture which would be expensive to run it that far. The yard on the side of her house wouldn't work because on one side is an unoccupied house with a water well with a non-functioning water pump. The inspector said the 100 foot rule still applies because there is nothing to stop the owner from installing a new water pump and using the well. The yard on the other side of the house was too close to adjoining property, even though it is just pasture there is nothing to stop someone from building a house there. So she had to have the sprinklers installed in her front yard. No huge deal, with a lot of visitors the sprinklers might occasionally come on for ten or fifteen minutes during the day. Just tell your guests "Oh those darn sprinklers" but don't tell them where the water is coming from!

I don't remember the price, just that it was a few thousand more than a standard system would have been. But she has to have inspections three times a year which she has to pay for. And eventually the various pumps will have to be replaced.

This is a worst case scenario that hopefully you wouldn't have to deal with, but you won't know until you check it out.

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This is only a partial answer to add one important consideration. I've been living in a house with a septic system for 15 years, it was installed at the time of moving in.

An important problem of septic systems is fat accumulation, over time they render the "infiltration chamber" or drain field ineffective by depositing a water-impenetrable layer on the soil interface. This does not seem to be well-known in my locale, so some builders do not account for it.

  1. The one important way to combat this, is to have a "grease trap" between your house and the septic tank. I guess this would be important to ascertain that this indeed installed. (A websearch will show many different designs.)

    As a secondary consideration, I can imagine a septic tank, having been specially designed for the purpose, trapping grease at that location, which might be a reason for frequent pumping: to get rid of accumulated grease. But we don't know the specifics of the house in question.

  2. The household needs to follow the practice of washing the minimum amount of fats and oils down the drain, e.g. wiping out pots and pans with a paper towel to absorb as much oil as possible, and not decanting deep-fry oil (or other oils, e.g. from dental oil pulling or the liquid from olives) down the drain, but discarding with the trash (soaked in a suitable absorbent medium or sealed in some suitable container).

I understand that it is possible to dissolve the fatty deposit in a drain field by applying hydrogen peroxide, but imagine that a sufficient quantity would be quite costly. Also I don't have a good idea about materials safety in such an application; perhaps a professional in the field might be much better to consult.

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    There is no need for a grease trap because a septic tank is a giant grease trap. They are built the same way.
    – user71659
    Commented Jun 14 at 4:48
  • @user71659 that depends a lot on the actual design of "a" septic tank IMHO - I've seen quite a few different ones. But that is included in my answer. In my case, I was initially advised to add a grease trap by a friend with some childhood experience of clogged drain fields, and who actually did a Master's thesis involving septic tank use in certain communities. The actual device in my case was fairly cheap and easy to install, so why not. Over the years I pulled enough gunk from it that I'm glad did not solidify in (and clog) the pipes between the house and the septic tank.
    – frIT
    Commented Jun 14 at 11:46
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Find out whether any local government authority (in New Zealand that is called a District Council) has any future plans that would impact the septic system. My sister and her partner bought a house with a septic tank, and later had a lengthy battle (which they won eventually) with the District Council. The Concil wanted to install an expensive alternative (which doesn't work very well for the folk who did sign up).

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