Pump problem

[marcusbryan]

Hi ,
I have posted this thread on the new members forum but haven't had any replies, not sure if this should have been posted here but if any one can help I would be extremely grateful.


I am new to the forum and would really appreciate some help with a job we are currently doing.
I have installed a new bathroom(where an existing was already) for a client and during the works they have got their plumber in to supply a pump to boost the supply to the hot and cold in the house.
The hot water cylinder and cold tank are on the first floor the same as the new bathroom. The plumber has fitted a negative head pump as there was not enough height on the tank to get a positive head pump to kick in for the shower head.
Before the work they had an electric shower and poor flow to the other taps etc for hot water.
The problem I now have is that when they try and start the shower or any hot water on the first floor in the morning or periods where it has not been used for a while they need to flush a downstairs toilet or run the kitchen sink also on the ground floor before the pump will kick in with hot water, although the cold works fine all the time.
The hot water downstairs and everywhere else then runs with a lot of splurging of air for a while and eventually is clear and all works fine until it is left for a period of time again and they have to go through the whole process again.
The plumber fitted a 2.5 bar stuart turner negative head pump, this is basically running the whole house bar a cold main to the kitchen sink.
I am not sure how air is getting back into the system once it has been cleared, could there be a problem with the way the pump is connected to the vent pipe on the cylinder? or is there a problem with the pump being upstairs and feeding a floor below as well? and is this size pump suitable for this type of work?
Any advice would be greatly appreciated ,

Many thanks

Marcus

​

 

[Cds]

Has the plumber fitted a surrey flange to the cylinder? If not I think air can be drawn in from the vent.

 

[marcusbryan]

Hi,

I am not completely certain what the surrey flange looks like but am aware of it. I think he has fitted one as the the take off at the top of the cylinder has been changed to allow for the hot supply to come straight out at the top for the pump. So I Believe the fitting he has put on there is the Surrey flange.

 

[Cds]

There must be air getting into the hot pie work. This can only come from the vent pipe or a leak. Perhaps post a picture of the connections it might show what the problem is.

 

[marcusbryan]

Thanks,
These were my thoughts because presumambly if there is no leak which there isn't the only other way for air to get in is via the vent pipe. Especially in view of the fact it only happens on the hot and not the cold.
I will take a photo tomorrow when back on site and post to see if it helps.

 

[WHPES]

What's the diameter of the feed pipe from the header tank? Increasing it to 28mm may fix the problem.

 

[marcusbryan]

I will have to check this tomorrow as well although from memory fairly certain it is 22mm.
How would this help?

 

[secret squirrel]

Hello Marcus,

I'm a little confused with one aspect of this problem. I don't think your a plumber but the house holder has called in a plumber to do the pump. Yet they've called you to resolve the problem.

If there was a bathroom suite there already and all you've done is replace it, presuming its ok the pump issue belong to the plumber?

Not trying to cause an argument or any more issues just interested.

 

[marcusbryan]

Hi Secret Squirrel,

I am not a trained plumber but have been doing bathroom fitouts for twenty years so am fairly competent from that point but never really get involved beyond that and bring in my own plumber for anything slightly more out of the ordinary.
However for this one the clients had their own plumber that they wanted to use to do the pump (don't ask me why) as a seperate piece of work.
I think they are of the opinion that it must be something my team have done as they know their plumber well so I am basically trying to be as armed with knowledge as I can to point the finger away from us.
I could of course just say it is not my fault but I am trying to do what I can to instill confidence and goodwill.
But will see how I get on!

 

[stevetheplumber]

id get a set of the manufacturers instruction of the internet and go back armed with the info to show whats wrong ive not seen a pump for a good few years that doesnt specify a essex or surry flange to connect the hot water som allow a connection in to the vent provided the vent is at 45 degrees and connection comes vertically down usually subject to min hight of tank etc

 

[justlead1]

Hi As [DLMURL="http://www.ukplumbersforums.co.uk/members/whpes.html"]WHPES[/DLMURL] has suggested. Increasing the size of the cold feed to the cylinder, will increase the residue head at the point at which the pump feed is taken off. (its pulling more water off than can be supplied by the 22 mm cold feed, a negative pressure (vacuum) will be relieved via easiest route. The vent Good Luck

 

[marcusbryan]

Ah I understand now why changing the 22 to 28 would help, that seems to make sense of course.
One other thing I forgot to mention in the original post is that if the pump is run for about ten to fifteen minutes it virtually dries up almost coming to a stop in terms of water flow to the shower etc. Surely it cant be emptying the cold tank and hot water tank can it?
Thanks for everyones advice so far has been really useful, very pleased to have found the forum

 

[justlead1]

Hi. As can be seen from the amount of threads on this site. The fitting of high performance showers/baths, without addressing the existing plumbing system that is intended to feed them, often results in dissatisfaction. However this fir coat no knickers situation can cost large amounts to rectify, and unless discussed at outset / design stage, puts the job well over budget. Changes the atmosphere /relationship with the client.
Good Luck

 

[marcusbryan]

Hello,
If anyone is interested I thought I would let you know what the problem with this pump turned out to be.

After much messing around we worked it out and all is working fine now.

The hot water cylinder is heated directly and only via an AGA which is on every day of the year.
There is no control for the temperatue to the cylinder via the AGA so we fitted a blending valve just before the pump so the temperature at the pump was below 65. This is the max stated operating temperature for the pump and previous to fitting the pump the water was at scalding temperature throuhgout the house.
So coming back to the pump the problem was occuring because the water in the cylinder was getting very airiated when left overnight and it was bubbling below the level of the surrey flange fitted.
So we took this off and cut in a new hot water outlet into the cylinder lower down and hey presto it is all working perfectly.
Obviously the surrey flange was still getting air into it because of the very high temperature from the AGA heating the cylinder without any control over the temperature.
The AGA site states that there is no way to limit the temperature to the cylinder so this is one to look out for anyone in future maybe!

Anyway thanks for all the helpful advice and am glad it is solved.

 

[Plumbstar Tom]

no such problem would have existed if the pump was fitted originally via an essex flange. Never a fan of surrey flanges for pumps, they are restrictive and let air in

Glad the problem is resolved

 

[secret squirrel]

Superb result. I have made a note of this...

 

[WHPES]

The normal way to limit the temperature of the water in the cylinder in such circumstances is to fit an extra thermostat which controls a pump to a couple of independent radiators. When the temperature gets above a set level, the pump kicks in and sends hot water from the primary circuit round the radiators which act as aheat dump, thus limiting the overall temperature of the cylinder coil.

Any blending valve used for an Aga system must be a high temp TMV. Many TMVs are only rated up to 80 degrees C inlet temp. (often solar types are used as high temp TMVs).