Help! Recirculating DHW problem

[IanMK13]

I've just moved house and need some help to sort-out my plumbing. The previous owner used a well-known domestic maintenance services company and they have left me with an unserviceable hot water system. They have fitted a shower pump with 15mm tails (installed via a Wessex Flange) to boost the water pressure in the hot and cold systems. However, if the hot water is turned on and the pump starts, the pump will not turn off again until the electricity supply to it is turned off again. From the photo below, it's fairly clear how the plumbing was originally connected. I am guessing that this was originally a recirculating system. However, the circulation pump (2nd photo) is on a 15mm feed from the side of the cylinder. How/where will this connect to the two hot feeds (one in 28mm, the other - with gate valve - in 22mm) ?



The isolating gate valves on the circulation pump appear to be shut off, but I believe they are seized part open. With the shower pump off and a hot tap opened, the outlet of the circulating pump and the 28mm feed both get hot. If the shower pump is then turned on, the outlet of the circulating pump gets cold and the 22mm feed (with gate valve) also gets hot. Where is this cold water at the circulating pump coming from? Also, there are gurgling sound with the shower pump on. Is air being sucked down the overflow?

Is my best bet to return the layout to the original configuration and restore the circulation pump? If I need to increase the water pressure for the top floor shower, say, without installing a separate feed (so negating the advantage of the circulating system) I could install a pump locally. Would I need to keep the Wessex Flange for this as it will restrict the total hot water system flow?

Is anyone able to provide any insight and advice?

 

[Simon F]

the bronze pump will be fitted as a return for hot water,
so if that is still open when the shower pump comes on it will stay on as it has a flow back down the secondary return.
it needs sorting so that the shower pump just feeds the shower,
or the secondary return is cut out

 

[lame plumber]

bronze secondary return pump should be on a time clock btw

 

[solutions]

They have fitted the pressure boosting pump in to the wrong portion of pipe work. Either have the secondary circulating pump (bronze pump) cut out or have the pipe work feeding the pressure boosting pump altered. Ideally the secondary return circulation pump would be left to run on its circuit and the pressure boosting pump would be fitted to entirely separated pipe work feeding only the shower. I am assuming the pressure boosting pump currently boosts pressure to all hot outlets. Unless pressure at the taps is particularly poor without the pump it is unnecessary to boost the taps.

 

[IanMK13]

The circulation pump is not presently powered. I tried isolating it but I suspect the gate valves don't close fully. It's the 2 large bore hot feed piles I don't fully understand and where the pipe from the circulation pump connects to them. I don't want to lift the floor to find out. What would I be likely to find if I did?
I'd figured that once the pump starts the water circulating in the system keeps it going (perpetual motion!?).
On balance, I think I'd prefer immediate hot water to high pressure. The pressure at the most distant point (the kitchen) is low at present (with the shower pump turned off). Hopefully this would improve sufficiently if I remove the constriction of the shower pump with its 15mm tails and have the circulation pump assisting flow.
There is a shower upstairs and downstairs. A compromise may be to take the side port of the Wessex flange to the upstairs shower only via the shower pump. I'll probably revert the system to it's original configuration first (with functional circulation pump) and see what's what then.
Since it's a vented system, I think my options are limited.

 

[solutions]

The hot pipe work out of the cylinder runs to your taps the furthest of which will have 15mm pipe work running back to the cylinder and in to the circulating pump where it is pumped in to the cylinder. The secondary return bronze pump pulls water out of the cylinder along the hot water pipe work out to the furthest tap and back to the cylinder through the 15mm pipe work. It does this to insure that hot water is waiting in the pipe work and can be drawn off without first clearing the pipe of cold water first. The bronze pump will not increase flow or pressure, it only circulates hot water between the hot cylinder and the furthest outlets essentially turning the pipe work in to an extension of the hot cylinder bringing the stored hot water significantly closer to its point of use.
The pressure boosting pump gas flow switches that sense the movement of water and turn the pump on to boost the pressure. With the current pipe work placing the shower / pressure boosting pump between the cylinder and the outlets served by the secondary return bronze circulator if the secondary circulator pump is turned on the pressure boosting pump will sense the flow and boost the pressure that is intended to come out of an outlet, instead it will follow the secondary return pipe work back to the cylinder losing vast quantities of heat a and cooling the cylinder along the way.
The 2 pumps can co exist but not with the pressure boosting pump in the secondary circuit. The pressure boosting pump would have to have a desperate draw off from the cylinder and its own pipe work to the outlet it serves or it would have to be plumbed to a branch off the secondary circulating pipe work.
Also plastic pipe work should not connect directly to a hot water cylinder I believe it should have a minimum of a meter of copper pipe first before transitioning to plastic. And no part of the secondary return pipe work can be in plastic as the manufacturers do not permit it.

 

[IanMK13]

Hi Solutions. Thanks for clarifying.
I originally mistakenly assumed the bronze pump pumped OUT of the cylinder until I read Simon F's comment a second time. This all makes far better sense to me now.
I'm still puzzled by the 22m pipe with gate valve though. Could there be 2 loops with the 15mm pipe Tee'd off to the far end of each? A bathroom, ensuite and shower room are all to to the south of the cylinder (across 2 floors about 4 metres away horizontally) and the kitchen is to the north of the cylinder with, perhaps, 15 metres of pipework to it. (Presently, with no pumps working, it take 4-5 minutes for the water to run hot in the ensuite in a morning. That's a lot of pipework to empty).

 

[solutions]

Yes you can have 2 loops but they are in effect just one loop going out to, and coming back from different outlets but the one pump circulates water through it all. The gate valves may be to increase resistance on the shorter loops to insure the pump circulates water to the end of the furthest outlet which it won't if there is a closer shorter loop around which to pull water. (all speculation mind, as no way of telling without being on site)

That automatic air release valve shouldn't be there either its as likely to allow air to be sucked in as it is let air out.

 

[IanMK13]

Yes - lifting the floor is the last resort ;o)
I don't know how the air release valve works but I loosened the plastic cap yesterday and a little spurt of air came out. I tightened it up again. Will this stop it working?
I tried wiring-up the circulating pump tonight but I suspect it is seized; the hot feed from the cylinder didn't warm up. It looks like I will need to fork out for a new pump.

 

[solutions]

Honestly Ian you need to find a decent plumber who can visit you on site and assess what's actually installed and advise your best coarse of action. You could spend a lot of time and money trying this and repairing that. You may be better off starting over or changing just a very specific portion of pipe work. With all the will in the world I and the other forum members can't make those assessments for you on the other end of a broadband connection.

 

[IanMK13]

Please don't be exasperated - that's what I plan to do; but easier said than done. I've had the wool pulled over my eyes too many times in the past by 'qualified tradesmen' that I need to be able to discuss the situation from a knowledgeable viewpoint so that I can assess their ability. Remember - the previous house owner thought he was doing the right thing by getting a plumber from a well-known national company and this is why I have a problem now. (The previous owner had been led to believe that the low pressure in the hot and cold systems was due to the house being at the top of a hill).
I've come here to get an insight into the situation and potential problems and I really thank you for that. While I am presently attempting to surmise the original configuration of the pipework (I have some formal engineering training in fluid dynamics), I was hoping that the experienced people here may be able to suggest what configurations may be found in practice. I accept that the layout of the house (which I briefly outlined) is a major consideration in this.
Thanks again for the explanations and assistance provided.

 

[solutions]

Please don't be exasperated - that's what I plan to do; but easier said than done. I've had the wool pulled over my eyes too many times in the past by 'qualified tradesmen' that I need to be able to discuss the situation from a knowledgeable viewpoint so that I can assess their ability. Remember - the previous house owner thought he was doing the right thing by getting a plumber from a well-known national company and this is why I have a problem now. (The previous owner had been led to believe that the low pressure in the hot and cold systems was due to the house being at the top of a hill).
I've come here to get an insight into the situation and potential problems and I really thank you for that. While I am presently attempting to surmise the original configuration of the pipework (I have some formal engineering training in fluid dynamics), I was hoping that the experienced people here may be able to suggest what configurations may be found in practice. I accept that the layout of the house (which I briefly outlined) is a major consideration in this.
Thanks again for the explanations and assistance provided.

No problem Ian,
If you post in the need a plumber section you may find someone on the forum close to you willing to put you in the right direction.
The likely hood is that there is low pressure because you have a cistern fed system that is driven by the height of the stored cold water cistern in the loft. So the pressure will be low to poor. If there is reasonable dynamic mains pressure at the property and decent flow, then perhaps consider changing the cylinder to an unvented system. An unvented system would supply hot and cold water at a ballanced 3bar (assuming incoming main pressure is at least 3 bar). 1 bar is the equivalent of 10 meters of head or cistern height. I doubt you have 10 meters between the bottom of your cold water cistern in the loft and your tap outlets meaning at best now without the booster pump you will have a fraction of a bar pressure.