Risk of septic system issue from a party?

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ANyder

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Looking for some advice. I'm having a party at a rental house with 30-35 attendees for about 4-5 hours. The septic system is apparently designed for 12 people (the house sleeps about 10). Party guests aren't staying over so won't be showering etc, but the 6 people renting the house will be staying for a few days before and after the party. I'm trying to understand the risk of a septic problem, as explained in this article: Additional water inputs from bathroom use during a large party without pre-planning can cause an unwanted surprise for your guests.

As I understand it, even too much water volume alone can overwhelm the system because it takes time to process and drain off the wastewater. Hydraulic overload seems to be the technical term. But how much time are we talking about? E.g. would showers taken the morning of, or day before, or multiple days before, increase the risk of a problem during the party in the evening? Or is several hours enough time for water to work its way through?

Aside from avoiding running a lot of water immediately before the party, and telling attendees to be conservative with water use and only flush toilet paper, is there anything else we can do to mitigate risk?

House is in a coastal area if that matters.

It's too late to rent a portable toilet unfortunately.
 

Reach4

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How long since you got your septic tank pumped? It is cheaper to do it too soon than too late. So while you are probably OK, there might be time to get it done in advance. If you don't know how often you get it pumped, consider doing that. Ask the operator how full it was, and set your calendar accordingly.

That said, I think taking showers several hours before should be fine. I do remember staying over with a relative, and the septic backed up. But I think that happened during the extra showering.
 

ANyder

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How long since you got your septic tank pumped? It is cheaper to do it too soon than too late. So while you are probably OK, there might be time to get it done in advance. If you don't know how often you get it pumped, consider doing that. Ask the operator how full it was, and set your calendar accordingly.

That said, I think taking showers several hours before should be fine. I do remember staying over with a relative, and the septic backed up. But I think that happened during the extra showering.

Since it's a VRBO house I don't know when they've pumped it and can't ask them to pump it. I guess my question really is: is excess water volume over a short period of time really likely to cause a problem or is that risk overblown as long as no one is doing laundry, taking long showers, etc. etc.?
 

Jadnashua

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Except when first installed, and after pumping, the tank is literally full all of the time. The waste goes in one side, the solids (eventually, fall to the bottom, and the liquids go out into the leach field. The long-term problem with too much activity at one time with high volumes is that it can wash some solids out into the leach field. The short-term problem is the lines may become full. How well the tank can separate the liquids from the solids depends somewhat on its size, and how full it is of solids.

When newly installed, they will usually require a perk test, which tests the ability of the soil (and thus, the leach field) to absorb those liquids. Over time, especially if overused, and lots of finer solids get washed out into it, they can plug up the soil so that it doesn't absorb as much.

The party probably won't be an issue, but it could be if there has been lots or recent rain and the soil is saturated...that will slow the absorption of the liquids, and in the worst case, back things up if the volume exceeds the ability of it to absorb what overflows into the leach field.
 

ANyder

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Except when first installed, and after pumping, the tank is literally full all of the time. The waste goes in one side, the solids (eventually, fall to the bottom, and the liquids go out into the leach field. The long-term problem with too much activity at one time with high volumes is that it can wash some solids out into the leach field. The short-term problem is the lines may become full. How well the tank can separate the liquids from the solids depends somewhat on its size, and how full it is of solids.

When newly installed, they will usually require a perk test, which tests the ability of the soil (and thus, the leach field) to absorb those liquids. Over time, especially if overused, and lots of finer solids get washed out into it, they can plug up the soil so that it doesn't absorb as much.

The party probably won't be an issue, but it could be if there has been lots or recent rain and the soil is saturated...that will slow the absorption of the liquids, and in the worst case, back things up if the volume exceeds the ability of it to absorb what overflows into the leach field.

Interesting. Thank you. What happens if the lines become full? Backing up into the house fixtures? And if so, is that a temporary condition (rather than something resulting in damage to the system)? I'm hoping that's unlikely to happen only from toilet flushes and faucet use. Is that the case? Thanks again.
 

Reach4

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VRBO house
Had to look that up -- vacation rental.

I don't know when they've pumped it and can't ask them to pump it.
You could ask them if the system is maintained. But there is not likely to be a problem. They should keep it pumped often enough. Identify the lowest drain (shower or tub likely) and check that drain occasionally if you like. Or don't. The odds of a problem from what you describe are low. As a homeowner or landlord, you worry that you will do damage to the leach field if you go way too long. As a renter, you just don't want to be stepping in in or grossing out your guests.
 

Jadnashua

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If you try to put more volume into the tank than the leach field can drain away, yes, the lines can fill up, and when you try to add more, back up, preventing anything from being drained or flushed. That's an extreme case. If you've had some local flooding because of heavy rains, the ground itself could become saturated, then, the system may not accept any new waste into it at all. If you've got standing water over your leach field, it's either from a storm, or the leach field is failing, or overloaded.

From a long-term issue, high volumes that don't allow the solids to settle, can cause some to be washed out into the leach field which isn't designed to accept any solids, or if any, not in high volumes. Eventually, those fine solids can literally plug up the grains of sand/soil and prevent it from absorbing much of anything, or at the beginning of it, slow that down. At that point, you might need to excavate, and replace the soil and the leach field. That usually takes years of abuse into a system that wasn't sized or maintained properly...not a one-time party situation.
 

Tuttles Revenge

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Is it really a good idea to have a party with 30-40 attendees in the current covid scenario? I have friends who attended a wedding 3 weeks ago and both vaccinated and both contracted Covid. I wouldn't do it.
 

Jeff H Young

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Is it really a good idea to have a party with 30-40 attendees in the current covid scenario? I have friends who attended a wedding 3 weeks ago and both vaccinated and both contracted Covid. I wouldn't do it.
Certainly I'm having greater concerns than say a few months ago our family has other concerns with illnesses such as covid , flu , or other easily spread things that have come up lately due to some of us at very high risk . So unfortunately our guard has been raised . lets stay healthy. darn thought we had this taken care of.
 

WorthFlorida

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Covid is more of a problem than a back up septic system. There are essential three different septic installations, one with the tank above ground, part way buried or completely buried and usually at the lowest end of the property, or the opposite side of where the well is. Most should have an air vent. Depending on the grade where the pipe runs from the house to the tank, if the tank fills up and the drain field cannot take up the waste water, it will flow out of the vent pipe if it is lower than the house fixtures. Usually is will not back up like a sewer system. If this property is very flat and there are fixtures below grade that uses a pump, the pump discharge will usually have a check valve so a backup may not inside the home. The acid test is when a toilet is flushed and it gurgles while try to flush and doesn't empty the bowl, that is a usually sign the drain pipe to the tank is full of water.

With that many people use paper plates and cups, etc. that will greatly reduce the waste water load. A dishwasher may use 10 gallons per cycle, a ten minute shower is about 2 to 2.5 gallons a minute. New toilets are 1.6 gallon per flush.


One person with covid can easily spread it to thirty people and it's pretty well been proven that it is transmitted through the air, not from touch. Those who have been vaccinated is not a guarantee you'll not be infected, it more that you will be sick but won't require hospizations. Those that have been vaccinated can still be a carrier of Covid-19 but won't show symptoms, asymptomatic.

We booked a cruise for Feb 2022 but with this delta variant, the wife is getting the jitters. We all want to get back to normal but we're not ready yet.
 

ANyder

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Is it really a good idea to have a party with 30-40 attendees in the current covid scenario? I have friends who attended a wedding 3 weeks ago and both vaccinated and both contracted Covid. I wouldn't do it.

The party is outside, and everyone is vaccinated. I'm still somewhat concerned about the latest trends but it just means we'll take more precautions like keeping a little more distance and wearing masks if anyone needs to be inside together temporarily.
 

Jeff H Young

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Good luck with party! its nothing but a guess if your renta house is able to handle it. there is no answer to that.
You were unable to rent a porta crapper your choice decision is made.

purse-holder.jpg
 

Tuttles Revenge

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For years our VW club held a campout the week after our big VW show as a way to celebrate a successful show. One year it was at the newly constructed waterfront home of one of our members and we had access to a real bathroom in the basement. Sometime around 2am someone woke me up that the bathroom was flooding. Later in the morning with the rather perturbed homeowner we started looking around at the septic system... nobody had ever turned the pumps on that carried sewage from the holding tanks up to the drain field...

A septic system should be designed to handle surge flow once in a while.
 

Taylorjm

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Does the owner of the home know your having that many day visitors at the home? I rent our vacation home by the week and we limit the number of guest to 10 including all day guests to make sure we don't have a problem with the septic system. I don't know of anybody that rents their home that would allow a party of 30 people to be there using the septic system. Most rental contracts will allow the owner to evict immediately if the number of guests exceeds those allowed on the property.
 

ANyder

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Thanks for the advice, all. Just to close the loop on this thread: had the party, no septic issues whatsoever.

Does the owner of the home know your having that many day visitors at the home? I rent our vacation home by the week and we limit the number of guest to 10 including all day guests to make sure we don't have a problem with the septic system. I don't know of anybody that rents their home that would allow a party of 30 people to be there using the septic system. Most rental contracts will allow the owner to evict immediately if the number of guests exceeds those allowed on the property.

Yes, the owners were aware; when we rented the house we negotiated a price for holding an event there. Thanks for your concern though!
 
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