Capitol wrote:
wrote:
Capitol wrote:

OK, I've escaped from picking plums, so back to plumbing!


I'd rather be picking plums than installing radiators, or dicking
around getting soaked trying to measure flow rates from body jets!

The 22l/m

flow rate corresponds to about a 3-5ft head on 22mm pipe.

this tells us

the problem is on the inlet side of the pump, as the flow rate with 3bar
head would be up to 400l/m!!! It is a 22mm inlet size pump isn't it?


400l/m wow that is a lot. Yes it is a 22m inlet size pump.

A

15mm inlet can't cope. It seems as though you are looking for a flow
rate of around 30l/m, which with your head would require at least 28mm
piping into the hot water tank from the loft tank and separately fed
28mm piping from the loft tank into the cold side of the pump. The
problem is probably coming from the hot feed out of the tank being in
22mm with a few bends in the way. A 90 bend corresponds to about 2ft of
piping if in copper and about 5-8 ft if compression.


I am using 22mm push fit and there is a 90 degree elbow and then it
goes into the pump, likewise for the cold. Maybe I could shorten the
pipe run and make it fall more than it currently does, I was wondering
about the fall its more like a 90 degree angle than a curve

If you are using push fit, then the input side flow rates will be much
worse than I have indicated, as the inserts will reduce the internal
pipe diameter to about 18mm, this will reduce the flow rates by about
60%! (rough numbers). On the info provided, as I see it you need to
forget about push fit on the i/p side and go to copper 28mm to give
yourself a chance.

I did wonder about those inserts! I will re-pipe in copper. I am still
reluctant though to install another flange and go to 28mm, I guess I
can always revert back to old configuration if I use up too much water
though.


What I would

suggest is that you double up on the Essex flange by adding a Surrey
flange and connecting the two together with 22mm, opening up to 28mm
where they combine keep the bends to a minimum, use street elbows if
possible and feed to the pump in 28mm as far as possible.


Why would I not use 2 essex flanges, what is the difference? So I would
just use a 22mm to 28mm T?

Yes, you can do that, but you are pulling water out of the tank at the
same level and I suspect that you would do better to use a Surrey
flange to separate the flow slightly, also, you will not need to punch
another hole in the tank. I'm convinced that you need to go to 28mm
copper and not pushfit on the i/p sides of the pump. The i/p to the hot
tank needs to be 28mm IMO.

Ah gotcha, the susex flange installs into the top of the cyclinder as
opposed to at the side. I definately wouldn't want to punch another
hole in the tank if I was going to revert back to my old configuration.


Are you suggesting I pipe the cold feed in 28mm too? and if not why
not, not sure I understand why it would just be the hot feed causing
the problem?

Yes, sorry if I was not clear, 28mm copper is required for both hot
and cold feeds through to the pump. Push fit 22mm is much closer to 18mm
than 22mm and will not give the flow rates with a gravity feed. The
relative head loss for 18/22mm is in the region of 10/3 for 10l/m flow
rates /100 ft of piping.

This on paper

and with a bit of guesswork will give you about 40-50l/m into the pump
which hopefully will be sufficient. I would add however, that if you are
using water at this rate, the chance of a hot shower lasting more than
5-10 minutes is pretty unlikely, also the loft tank will empty, as the
inlet valve almost certainly can't deliver more than 10l/m.


The cold tank is a seperate one for the shower. I am a little worried
about the hot water supply as SWMBO takes forever in the shower or used
to

Maybe she'll get used to cold showers!!

Maybe she wont have a choice

Does this mean that you have
two loft tanks, one for hot and one for cold? If so , what are their
capacities?

I have a seperate 25 Gallon cold water tank for the shower, this was
used to feed an old power shower prior to our occupancy and just a hot
water cyclinder which is a standard size as far as I can tell. Looks
like all the others I've seen in the past.


Maybe I should try shortening the hot water feed to the pump first and
then go the other route? how does that sound??


I'd grasp the nettle and replumb almost all of the input feed system in
28mm copper for both hot and cold supplies, with a Surrey flange and an
Essex flange using 22mm then 28mm copper until just before the pump. It
must be easier than messing about with lots of plastic pushfit which can
never work IMO.

OK I'm going to take your advice, but I'm going to try 22mm copper
first and then if no joy make the move to 28mm and an additional
flange.

Just as a check, I ran a flow rate of 15l/m from an approx 10mm dia
outlet with a system fed as I have described. This corresponds to a head
of about 10ft at the outlet point, with an input head of 100ft!
For your 22mm outlet, this would become 60l/m if the scaling is
applicable, hence my estimate of 40-50l/m

Brilliant, thanks so much again, another job on the list for today!

Cheers

Richard


Regards
Capitol