Moreover, why is the pump on the return? This would mean that it is sucking water around the system. Also, if what you mean by "pumping into the tank" is that water comes out the vent, you have put the pump in the wrong place.
Many pumps are on the return side, and on some new installations. In general its not necessarily a definite cause of a problem.
Also, have you installed the system yourself. If you have, you are a bodger and you should stay away from it in future.
markd, take no notice of this it's one of sterose's stock joke lines. If you take offence the next line is to tell you have no sense of humour.
:
Incidentally, use capital letters (e.g. for names) in your post - it makes overall reading easier - instead of just a lump of, what appears to be, a non-descript jumble of letters.
Surely not sterose, after all you made sense of it and even managed to give a reasonable piece of information in your first paragraph, (it just went downhill from then on). markd did have enough commas and a question mark which helped.
Are you having a bad day? There was a short period where your posts were becoming quite helpful, but you seem to have got back to the old vitriol, where reason gives way to verbal violence (or have I just missed the subtlety of another sterose wittisism mmm?
: ).
Now, here is a non-descript jumble of letters:
kjsdhnughuryouhf jhfbcuyegfurohfmoidfsdhgfxbueyriurmcrpimkfkhdueie875tono4yc94497yb49797y97yt9cn7y9785yt97nf pirfcm094,9,9i,c-439mn9 y945yb 974yn 084nc97q3tyb 79q384yu0 8 u5087n0 8yu5tm0ump ut40 fu2.