RJHumphrey Posted April 19, 2022 Share Posted April 19, 2022 Hello, just wondering about others thoughts on my current predicament. I have installed a Marsh Ensign 6 sewage plant and poured concrete up to the outlet level, as per installation advice, but now slightly confused on my next steps. In the installation sheet supplied it states if the ground is free draining, pea shingle can be used to backfill around the tank, but I have some concerns, obviously above the outlet level the tank is not provided support from the water inside, I also plan to use the supplied manhole riser which could add up to 1m of additional weight on the sewage plant from backfill to reach the cover height. Am I worrying about nothing? I did contact the manufacturer for advice, but felt a little fobbed off with their response, ‘as they can’t comment on individual sites as the ground conditions all differ’ I have visions of adding the backfill and the tank imploding, any advice gratefully received. thanks, Ryan Link to comment Share on other sites More sharing options...
SuperJohnG Posted April 19, 2022 Share Posted April 19, 2022 It'll be fine. They are meant to be buried so can take it, backfill with peashingke or just earth which would be much cheaper! Link to comment Share on other sites More sharing options...
ToughButterCup Posted April 20, 2022 Share Posted April 20, 2022 11 hours ago, RJHumphrey said: ... Am I worrying about nothing? ground conditions all differ’ I have visions of adding the backfill and the tank imploding, any advice gratefully received. ... No, you aren't worrying about nothing. You are understandably concerned. First, backfill: the pressure of the backfill is designed in to the product: think about it for a moment - if it weren't , the tank - ie. not just yours , but all tanks - would implode. And thats a sh1t situation to be in as a manufacturer. The manufacturer is correct ground conditions do differ: but theirs was a mealy-mouthed response. They could have asked you what your ground conditions are - the one thing to be concerned about - slightly - is the water table. A high water table means a higher likelihood of a buoyant tank. Yes, improperly anchored, they do pop out of the ground. Spectacular when you see it happen. IF thats the case for you ( high water table) , then simply anchor the tank with (say) a cubic meter of concrete , and top off the rest with normal backfill . We did, and for good measure threw in some concrete fence posts at the bottom of the pit, chained them to the periphery of the tank, a bit like an emergency anchor for a boat. Our poo tank is going nowhere in a hurry. Makes for a really secure feeling that when seated on the throne. Link to comment Share on other sites More sharing options...
Russell griffiths Posted April 20, 2022 Share Posted April 20, 2022 (edited) I backfilled with gravel as per manufactures details, I looked at it for a week then took 300mm out and capped it off with 150mm of concrete, mine will never be driven over, but I liked the security the concrete provided. Edited April 20, 2022 by Russell griffiths Link to comment Share on other sites More sharing options...
joe90 Posted April 20, 2022 Share Posted April 20, 2022 I backfilled up to outlet with concrete as I have a high water table, topped off with gravel to stop flooding with heavy rain. Link to comment Share on other sites More sharing options...
RJHumphrey Posted April 20, 2022 Author Share Posted April 20, 2022 Thanks for your replies, I would have been more comfortable if I wasn’t adding the chamber riser (supplied by the manufacturer) so approx 1.5 metre of backfill on top of the tank. The tank isn’t going anywhere as enough concrete has been poured to secure it in place, up to the same level as you Joe90, where there is a route for any groundwater/ rainwater to naturally flow away, just concerned about the additional weight required to bring the ground level up to chamber level. I have phoned the supplier who is putting me in contact with the rep, but can’t see him knowing much about installation, may be proved wrong. Did think about adding lintels across the tank to support the weight, but is this overkill, and are these designed to be in the wet ground for years, if they were to fail it would be game over for the tank. Link to comment Share on other sites More sharing options...
joe90 Posted April 20, 2022 Share Posted April 20, 2022 22 minutes ago, RJHumphrey said: Did think about adding lintels across the tank to support the weight, but is this overkill, I would say yes, if they were required then the installing instructions would say so surely, as long as you follow the manufacturers guidelines then you are ok, if they are unclear demand they confirm how it should be installed. Link to comment Share on other sites More sharing options...
Russell griffiths Posted April 20, 2022 Share Posted April 20, 2022 I thought this was the best way to spread the load of additional soil. Link to comment Share on other sites More sharing options...
RJHumphrey Posted April 20, 2022 Author Share Posted April 20, 2022 Yes Russell Griffiths, that removed the worry of additional weight on the tank. Did you pour this in stages. Link to comment Share on other sites More sharing options...
Russell griffiths Posted April 21, 2022 Share Posted April 21, 2022 9 hours ago, RJHumphrey said: Yes Russell Griffiths, that removed the worry of additional weight on the tank. Did you pour this in stages. Nope just one pour. Link to comment Share on other sites More sharing options...
RJHumphrey Posted April 21, 2022 Author Share Posted April 21, 2022 2 hours ago, Russell griffiths said: Nope just one pour. What Sewage treatment plant did you install? Link to comment Share on other sites More sharing options...
Russell griffiths Posted April 21, 2022 Share Posted April 21, 2022 2 hours ago, RJHumphrey said: What Sewage treatment plant did you install? Graff. Link to comment Share on other sites More sharing options...
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