low pressure problem - please help!

[Capitol]

Just go away and try to do it. Then you'll find out.

Regards Capitol

[Doctor Drivel]

"robgraham" wrote in message news: [e-mail]...

[robgraham]

Now, now - political rants are no better. Definitely OT and don't help the rest of us get the answer we want.

Rob

[Doctor Drivel]

The LibDems are going to lace them anyway, and knock them into 3rd place, and about time too.

[mike]

Capitol wrote

As it happens I've done it, a couple of years ago, and I'm a complete amateur.

[Capitol]

dIMM is the problem. Christian has already pointed out that the pump will cavitate if the input flow is too low. If the pump cavitates, then the pressures will not equalise correctly(ie fast enough). If you attempt to feed a bath and a shower from two points of the same cylinder at the same time ( particularly via a Surrey flange), with a pump sucking on one of them, the odds are that the pump will not have enough input flow producing cavitation, a pressure equalising valve cannot cope with this (you will see that the description says "CAN turn a manual shower into one which doesn't suffer temperature fluctuations--- not WILL") . The other problem which you will probably see is that the cold water intake into the tank will be too fast and the hot water in the tank will not stratify correctly. The result will be a shower which has very erratic temperature characteristics, as even with a thermostatic mixer the required correction is just not fast enough. That's before you start to look at the size of the feed pipes and the required head/flows. The Surrey flange will not work correctly if there is not enough input flow into the tank.

Interesting that Grundfoss show an Essex flange in their drawings, These give more flexibility in positioning and higher flow rates. dIMM couldn't possibly accept that Essex was a better proposition!

You can't solve a problem until you define it, this had not been done.

Re -reading the thread, my impression is that the OP may have in all probability a basic flow problem into/through or out of the hot water tank. Even nastier, the feed pipes from the hot water tank to the rest of the house may be furred up (downstairs flow is also poor). Is it a hard water area? Is there a loft tank feeding the hot water tank? First steps are to check the pipe sizes, hot water feeder tank size and position(height primarily) and then to measure the hot and cold flow rates at the bath/sink taps and the kitchen hot tap. Distance flowed would also be useful in the case of the hot. Given this information, there is a chance that the first step required would be to replace some pipework and/or some valves. Pressure equalisation may well be a good idea, but do bear in mind that it is not the answer to all problems. Pressure reduction may be an equally valid approach. Roger's experience is valid in that often you can get away without Surrey/Essex flanges, particularly if you are a small household and the shower has a fairly low flow rate. For very high flow rates multiple flanges can be a good idea.

Using a low pressure booster pump as a panacea will not solve the problem if it is elsewhere. The pump could in some cases give a head below about 12' if mounted at bath floor level. Shower pumps normally give heads of 20--80'.

This thread had lots of advice, some very poor due to inexperience (dIMM) which probably would not solve the real problem.

That's why the thread was not worth keeping.

Regards Capitol

[timegoesby]

< cut >

I was the one who said he would keep the post. The point of using a small quiet pump fitted in the pipe, possibly near the shower mixer, not on the floor, with a mixer with a pressure equalizing valve using the cold mains as the cold feed is very sound indeed. And very appealling. Two have said they have already done it and it works and that is good enough for me. This pump has 1/2" connections and is unlikely to drag all the water out of the cylinder and only suitable for one outlet point like a shower. It will suck out of the cylinder and down the cold feed from the cold tank. If this is 22mm pipe then I can't see a problem. If it doesn't work then you are right in that there is a problem elsewhere, like a blockage. The only dim one on this thread is you and you have a clear attitude problem.

[robgraham]

Thanks for that - slight pity you didn't give us that the first time as it gave Drivel an excuse to pollute the air with his political dribblings.

Having also reread the initial posting, I would agree with what you are saying; it would seem that the OP's dhw system has a fault in it that is creating the low pressure - either due to the configuration, or to furring up or the likes. A pump therefore is not going to solve his problem as the feed - either out of the hw tank or into it from the cw tank - just in't great enough. Cavitation will result.

I am expecting that my set-up - 28mm feed to hw tank and seperate 22mm feeds to bathroom and the rest will be ok with the Grundfos pumpin the 'rest' feed. The requirement is to overcome a 2.5m head to the kitchen where her-in-doors had me fit a continental style spray mixer tap which is on a shower head type hose and consequently a high pressure drop.

Rob

[mike]

robgraham wrote

I'm sure this will work, it's just like mine except I've only got a22mm pipe to the HW cylinder.

Restrictions down the line, plus the cold water feed is as clear as I can make it, make it work fine.

I would be interested to hear if your showere tap wrks well, when I had one, a year or so prepump, it was useless, but I like them, and ir=f you get a fairly brisk shower I'd be tempted to get another one

[manatbandq]

LOL!

Didn't you notice the drunkard falling on the self destruct button as he staggered out of office?

[robgraham]

I'll report back in due course - may be a rather long 'due' though, with the schedule as it is at the moment !

Rob

[Doctor Drivel]

I think it's a good laugh too.

[Doctor Drivel]

Read what I write and learn dumbo.