Very common dilemma Todd. A good available water test and a careful pump
selection should get you to within 5 PSI of your design but if you're too
close to call, then you have to design for 175+ PSI. When's the last time
you rejected a pump for over pressure at churn? You can do that. Just like
not meeting design. If you specify a pump with 110% churn and get a
submittal "and" it doesn't make it (either); tell him to take it back or fix
it. I have and have seen it before. You're performance compared to design
is only as good as your data. A good flow test or 2, maybe a hockey puck
ditson reader for a week's sampling, a knowledgeable pump selection and not
too many extra elbows to get the system installed and your testing results
should reflect your hydraulics very closely.
Tom
I seem to be running into several situations lately where there is a very
fine balancing act between meeting the 100 psi at the top outlet of the
standpipe and not exceeding 175 psi at the base of the riser. (6 story
hotels are a good example) Does anybody have any good ideas they'd care to
share on making these work? I'd like to limit the use of extra-heavy pipe
and fitting (especially larger sizes) and PRVs. I have several tricks up my
sleeve, but I'm running out of sleeves.
Todd
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