sump cracked, maybe uneven ground

[henward]

what ways are there to avoid making a frame.

if i use a very thick layer of poly, will this work? say 50mm poly?

or do i need to make a frame and poly on top to avoid a crack a gain?

i have had this sump on the ground with a 20mm poly an dnever had issues, recently i added a second sump sitting on top of the sump as a trickle, i would say the weight probably contributed to the imbalance of the weight.

if i get another sump, what easier methods can i use to 'even' out the ground instead of using a frame?

or is a frame really the only way?

looking for least path of resistance.

[rabid]

slab of 19mm mdf cut to sump size with 20mm poly on top? They will cut it at mitre 10 etc.

[livingart]

size of sump

as you have said adding tower has changed stress points on glass

more weight on one end can affect compression on the poly

100mm maybe better

[disgustipated]

why not make a simple, cheap cinder block stand with two pices of 6x2 running lengthways.

[henward]

i was thinking a square timber frame, some middle bits going accross. and then poly or mdf on top.

i think mdf would be better than poly as it is stiffer.

options:

1) timber frame - mdf on top or poly

2) 50mm poly

3) 2x 20/25mm mdf no poly

4) 25mm poly on top of mdf or reversed

what would be better ?

[disgustipated]

doesn't mdf turn to soggy weetbix when it gets wet?

[livingart]

15mm ply

[JaSa]

Don't go thicker with your poly - it will be worse !!!

If you put weight on polystyrene, it "compresses" most around the sides because that is where the material can escape the pressure coming from top. On the other hand, in the middle the polystyrene can't go anywhere and you will end up with a slight hump in your sheet under your tank. The thicker the sheet and the bigger the tank (weight) the bigger this effect. Means, thick sheets put more pressure on your tank and totally fail the purpose - wich is to level out LITTLE irregularities in the surface of the stand / base. No tank needs more than 10mm of polystyrene to do this job...

Cheers,

JaSa

[jackp]

depending on how uneven the surface is, you may find that mdf will slump to the same shape (particularly if it gets wet). Treated ply would be better. Might even pay to bed down the ply with adhesive so there are no gaps underneath. You can also get a product known as self-leveling compound. you could use this to even out the surface and then just use poly

[blueether]

I think I would be tempted to put a very low stand (4x2 length ways and 20mm ply on top) and sit that on top of a sheet of PVC (or anything very thin and waterproof) then run thick beads of no more nails along the undersides of the 4x2 and then sit that on the PVC.

Side on:

|        SUMP            |

|                        |

|________________________|

######################### <- poly

=========================  <-ply

+++++++++++++++++++++++++ <- 4x2 stand, only 2 or 4 inchs high

========================= <-no more nails, then pvc underit all


End on:

|  SUMP      |

|            |

|____________|

############# <- poly

=============  <-ply

++   ++    ++ <- 4x2 stand, only 2 or 4 inchs high

==   ==    == <-no more nails, then pvc underit all

[David R]

There is no other option than the timber frame, except maybe a steel frame. A glass box filled with water needs an even foundation to sit on, ply or mdf or poly won't provide that by themselves.

Actually, the other thing you could do is pour a small plinth of self levelling concrete, though that would be more hassle than a timber frame...