Costly Home Rental Experience
The Grants own a home in the beautiful Constance Bay area on the outskirts of Ottawa, Ontario, Canada. They rented their home while working out of country for several years. Unfortunately, their tenants did not have a vested interest in ensuring the home’s septic system remained healthy. Unchecked overloading eventually resulted in system failure which required complete replacement. A new Clearstream onsite sewage treatment system was installed in 2012 and expanded in 2015 to accommodate an in-law suite which was built onto the residence.
The new onsite system consists of a 3600 L (950 gal) septic tank followed by two 600N Clearstream units installed in parallel. Flow through the entire system is by gravity. Treated effluent from the Clearstream units flows through a filter vault and then into a raised area bed of clear stone overlying a 45cm (18″) thick layer of clean sand. A 300mm (12″) thick sand layer “mantle” extends for a distance of 15m (49ft) beyond the stone bed. The slope of the subgrade below the sand layer was designed to be 2%. The underlying native soils are considered impervious (i.e. slowly permeable, clayey soils).
High Level Alarms With Replacement System
Since the expansion, the Grants have experienced periodic high level alarms and backflow from the area bed into the Clearstream units and septic tank. Sometimes it was observed that the effluent in the filter vault was not very clear and/or there was “gunk” in the water. This has often coincided with snowmelt and rainfall events. Considering the significant investment they had in their new onsite sewage system, the Grants were concerned about the potential for another septic failure and sought to better understand what might be causing the high levels.
SepticSitter System Retrofit
A SepticSitter system was retrofitted on April 18/18 when non-contact sensors were retrofitted to three locations:
- Septic tank
- Filter vault containing a Tuf-Tite commercial series EF-6 filter (1/16″ screen size, rated at 1500gpd)
- Area bed – an inspection port was added to the area bed. The bottom of the port is approximately 10cm (4″) below the bottom of the stone layer (i.e. into the clean sand layer).
The screenshot below shows effluent levels for the two month period since the sensors were installed.
On April 18 when the inspection port was retrofit to the area bed, the effluent level was observed to be above the top of the clear stone layer. Effluent from the area bed appeared to be backflowing into the filter vault as the inlet and outlet piping and filter in the vault were submerged. Effluent would also have been backing up into the Clearstream units at this time. There was scum material floating on top of the water in the filter vault.
SepticSitter Onsite Insights
Some interesting observations can be made from an examination of the SepticSitter data in the two months following retrofit of the monitoring system.
- Baseline levels in the filter vault returned to normal, dropping approximately 15cm (6″) between April 18 and 21. This was likely due to a drop in the area bed levels so that it was no longer backflowing into the filter vault and Clearstream units.
- Surges in filter vault levels (occasionally to the point where effluent would be backing up into the Clearstream units) occurred between April 21 and May 7. These surges appear to have coincided with peak water usage (sewage output) from the home, and typically only lasted 2 to 3 hours before levels returned to the normal baseline.
- On May 7, the Grant’s septic service provider visited the site and carried out routine preventative maintenance which included cleaning the Tuf-Tite EF-6 filter in the filter vault. Evidence of this maintenance event can be seen in the graphed data as baseline water levels in the filter vault immediately dropped about 2 to 3cm on the day of the service visit.
- Baseline levels in the septic tank also dropped about 3cm immediately following the service visit. This difference may be due to effluent previously being restricted at the filter, so that it was backing up all the way through the treatment system to the septic tank.
- Short term “usage” peaks in the filter vault levels were higher, ~12cm (5″) before filter cleaning, but only 5cm to 6cm (2″) after. This is probably due to the recently cleaned filter not presenting as much resistance to flow.
- Throughout the month of June, the magnitude of the filter vault usage peaks seem to be increasing again, although as of June 18, they are not yet peaking to the point where the vault would be backing up into the Clearstream units.
- A total of 34mm (1.3″) of rain fell in the area on April 25, 26 and 28th. Levels in the area bed (which had been steadily dropping) rose on those days and then resumed dropping.
- Water levels in the area bed continued to go down until they fell below the bottom of the clear stone on May 11. They generally remained at or below this level, apart from significant rainfall events such as the 53mm (2″) which fell in the area between June 3 to 7.
Although it has only been two months since retrofit, the data being recorded by the SepticSitter system is already providing significant insights to better understand the status of the Clearstream and area bed and to identify factors which may affect the short and long term operation of the system.
- The area bed seems to be subject to saturation and excessive ponding in the spring in which effluent combined with snowmelt and rainfall cannot drain away from the bed as fast as it enters.
- When levels in the area bed clear stone layer rise higher than 20cm, this appears to cause backup into the filter vault.
- Excessively high filter vault levels have caused effluent to back up into the Clearstream units and septic tank, raising levels above normal recommended operating levels. This has likely interfered with proper treatment in the Clearstream units as indicated by the presence of floating scum in the filter vault.
- The effluent filter appears to be quickly re-establishing a clogging layer within a couple of months of cleaning. While the levels in the filter vault have not reached the point of back up into the Clearstream units again, the data shows it is trending in this direction.
- The area bed appears to drain down quickly in the late spring after which it appears to have ample capacity to handle the daily flow of effluent, and to absorb heavy rainfall events.
- Various warning and critical alerts have been set up in the SepticSitter web application which will automatically send out email notifications if levels rise above these presets. For example, a notification has been set for the filter vault if levels rise to the point of backing up into the Clearstream units. If filter vault levels are excessively high but area bed levels are observed to be normal or low (i.e. below ~20cm), this probably means that the effluent filter requires cleaning.
- If effluent filter cleaning is required too often, consideration could be given to changing to another type of filter with more surface area which may provide a longer time between cleanings.
- The reason for the excessive ponding in the area bed in the spring of the year is yet to be determined. One theory is that water is getting trapped in the sand layer at the downslope toe of the sand mantle. This could be due to slowly permeable soil (clayey soil or clayey topsoil) having been placed at the toe of the mantle. This could be creating a dam effect preventing effluent and water from draining away quickly enough in the spring. Ongoing monitoring throughout the year will help to confirm what is happening and identify potential corrective action.
- To confirm or disprove the theory of water getting trapped at the toe of the mantle, an additional inspection port should be installed to the bottom of the sand layer near the toe of the sand mantle. This would allow the installation of another SepticSitter sensor, or at least periodic manual measurement of water levels in this location.
The homeowners are pleased with the insights provided by the SepticSitter system so far.
SepticSitter is an ideal solution for anyone renting out their property – house or cottage – so you know ahead of time that a problem is starting and you aren’t blindsided by a catastrophic failure requiring a complete rebuild. Had we seen the data indicating that the health of the system was failing, we would have had an opportunity to educate long term renters or potentially deal with the impact left from short term renters. A relatively small investment in the SepticSitter system would have provided us with a significant insurance benefit against having to spend 20-30 times more money to rebuild the system.
Septic professionals: What insights have you observed in the data shown above?
Do you have a different theory about why the area bed is ponding excessively in the spring?
What are your thoughts on the filter clogging? Do you think the 1/16″ screen size is too small?
Share your thoughts in the comments below!